n1das

DCS is transmitted at a rate of 134.4 bits/s.  The DCS waveform directly modulates the FM carrier, with a logic 1 represented by a positive carrier shift and a logic 0 represented by a negative carrier shift.  The FM deviation is about the same as CTCSS/PL.  The DCS waveform's edge rates are carefully controlled to limit harmonic content to avoid generating audible harmonics.
 
A DCS word consists of a 23 bit cyclic Golay code with 12 bit codeword (23,12) formed from the 12 least significant bits.  The 11 most significant bits are error correcting code bits generated by the Golay algorithm from the 12 codeword bits.  The 12 bit codeword consists of a fixed Octal 4 (100 binary) plus the 3 Octal digits that you can program.  A DCS word plays out backwards over the air due to the least significant bit being transmitted first.  A DCS word is sent repeatedly as a continuous low baud rate data stream.
 
DCS/DPL has a specific turn-off code or reverse burst at the end of a transmission which resembles a 134.4Hz sine wave.  In radio systems with a mix of CTCSS/PL and DCS/DPL usage, it is recommended to avoid using a CTCSS/PL tone of 136.5Hz due to the DCS/DPL kerchunk problem caused by the 134.4Hz DCS reverse burst.
 
The time required to reliably decode DCS is slightly longer than CTCSS and is about 350ms or less.  CTCSS typically decodes in about 250ms or less.  When decoding DCS on very weak signals, the DCS decode threshold can be as much as 2 dB worse than CTCSS.  From an end user perspective, these differences are way down in the noise (LOL) and it's hard to tell any difference.  The average end user probably won't notice any difference in DCS/DPL vs. CTCSS/PL performance.
 
DCS has its own set of issues to deal with.  The long high and low bit times of the NRZ data can cause problems with baseline wander and cause decode problems.  Distortion in the transmitted DCS waveform itself can cause decoding problems in the receiver.  DCS is also sensitive to frequency errors in the transmitter and receiver.  A signal transmitted with DCS received a few kHz off-frequency in the receiver impresses a DC offset on the recovered DCS waveform which causes the decoder to see a step function instead of the DCS data.  This causes very slow decoding or failure to decode.  Good low frequency response down to about 3 Hz in the modulator in the transmitter and in the discriminator output in the receiver are necessary for reliable DCS operation. IIRC phase modulated systems have trouble with DCS.  True FM modulated systems tend to work better.
 
Motorola trademarked the Digital Private Line (DPL) name.  Other manufacturers have to call it something else.  Digital Coded Squelch (DCS) is the generic name.  You'll see mixed usage of the two names as I have used them above. If it's not a Motorola radio, it's not DPL. It's DCS instead even though it's exactly the same thing as DPL.  Motorola originally implemented 83 DPL codes and manufacturers have expanded the set of codes to 104 codes.  Motorola's 83 DPL codes have been implemented by all manufacturers but not all manufacturers have implemented the full set of 104 codes.  Motorola's original set of 83 DPL codes have been fully vetted and are known to work well.  Some of the extra codes making up the set of 104 codes may not work as well.  YMMV.
 
I've also heard DPL sometimes referred to as "Definitely Prevents Losers". LOL.  I successfully thwarted a GMRS repeater jammer years ago with DCS/DPL so the jammer couldn't key my repeater.  The jammer didn't have a clue about DCS/DPL nor did he have DCS/DPL capability in his antiquated equipment and only had CTCSS/PL.  The jammer eventually gave up.  This trick won't work anymore given that practically all manufacturers now offer DCS capability in their radios.
 
DCS information:
https://wiki.radioreference.com/index.php/DCS
http://onfreq.com/syntorx/dcs.html
http://www.repeater-builder.com/tech-info/ctcss/ctcss-overview.html

Below is general information on the Motorola DTR and DLR series 900MHz FHSS digital radios.  I am a user of the DTRs and the DLRs and have become a serious fan of them because they are professional quality and work amazingly well.  I own a small fleet of legacy DTR650 radios and a small fleet of DTR700 radios.  I have also previously owned a small fleet of DLR1060 radios.
 
DTR600/700:
https://www.motorolasolutions.com/en_us/products/two-way-radios/commercial-business-two-way-radio-systems/on-site-business-radios/dtr-series.html
 
DLR1020/DLR1060:
https://www.motorolasolutions.com/en_us/products/two-way-radios/commercial-business-two-way-radio-systems/on-site-business-radios/dlr-series-digital-radio.html
 
CPS download:
https://www.motorolasolutions.com/en_us/products/two-way-radios/commercial-business-two-way-radio-systems/on-site-business-radios/dtr-series/dtr700.html#tabresource
The Motorola Business Radio CPS is a free download from Motorola and programs all of their Business Radio models.
 
CPS cable on Amazon:
https://www.amazon.com/Motorola-HKKN4027A-Programming-Cable-Black/dp/B00EC2PV6A/ref=sr_1_1?dchild=1&keywords=motorola+HKKN4027A&qid=1613093281&sr=8-1
The same CPS cable is used for programming all of Motorola's business radios.  The one exception is the legacy DTR410/550/650 models because they use a different CPS cable.
 
No programming is needed to use these radios out of the box at the factory default settings.  The DTRs and DLRs work with each other right out of the box at the factory default settings.  Customization of settings and features requires the CPS.  Some settings can be changed without the CPS.  The fastest way to get some DTR and DLR radios talking to each other if they don't already do so is to reset all of them to the factory default settings and then go from there.  You don't need the CPS or the cable to get started with the DTRs and DLRs.  Motorola has made it insanely easy to get started with them.
 
Motorola DTR550 case study:
https://www.motorolasolutions.com/content/dam/msi/docs/business/_documents/case_studies/rutland_healthcare_case_study.pdf
 
The Rutland Healthcare case study is a bit dated as the DTR550 was used.  The legacy DTR410/550/650 models have been on the market since 2006 and were discontinued in November 2018, marking the end of a 12 year production run.  Support for the DTR410/550/650 models end on November 30, 2023.  The DTR600 and DTR700 are the replacement models for the legacy DTR410/550/650 models.
 
DTR history:
https://en.wikipedia.org/wiki/MOTO_Talk
 
The DTRs and DLRs are a spinoff from Motorola's MOTOTALK feature in several NEXTEL iDEN phones years ago.  NEXTEL called this feature Direct Talk and is not to be confused with the DirectConnect PTT feature which worked through NEXTEL's iDEN network.  The DirectTalk feature works PTT simplex phone to phone on 900MHz and uses FHSS.  The killer app for this feature is for PTT use between phones when network service is spotty or unavailable and phones are close enough to each other to communicate.  NEXTEL phones were popular with contractors and other professionals at jobsites and there was nothing more frustrating than the DirectConnect PTT feature would not work because one or more phones had no network service and phones were still relatively close to each other.  The off-network DirectTalk feature provided a solution.
 
The DTRs and DLRs use the same FHSS system but were coded differently from the phones to be incompatible and supposedly was done on purpose.  The DTRs and the DLRs are the modern day implementation of the MOTOTALK platform.  The legacy DTR410/550/650 models shared a common design with a NEXTEL phone during development and were originally part of the same design project until they spit apart to become separate products.  Users of the legacy DTR410/550/650 models will notice that they are very NEXTEL-like in their behavior.
 
The DTRs are commercial radios and loaded with features for business radio users.  However, they often are too much "radio" for the average retail business user.  Retail users just want a small radio with no keypad and display and minimal features to keep it simple.  The DLRs are Motorola's answer to that.  DLR = Digital Lightweight Radio, according to Motorola.  The DLRs have the features of the DTRs, minus a display and keypad and channel capacity but are compatible with the DTRs.  The DLRs were released in the summer of 2015.
 
The DLRs are incredibly easy to use.  The DLRs appear to be marketed toward users of the UHF analog CLS series analog business radios that are very popular for retail use.  The DLRs seem to make sense for the target market.  Some people don't like the large round PTT button on the front of the radio because they are so accustomed to PTT being on the left side of the radio.  The DLRs are smaller than most FRS bubble packs and the front button makes sense for the very small size and thin form factor.  A DLR radio is comfortable to hold in either hand and a thumb press activates PTT.  I found the round front PTT button makes perfect sense for such a small radio.
 
Old retired NEXTEL phones with the off-network DirectTalk feature can be found very cheaply on eBay.  The i355 is a good model to look for.  There are several videos on YT demoing their use.  Factory fresh new batteries are still available for them.  I know that because the legacy DTRs use the same battery and I recently re-batteried my DTR650 fleet.  The one gotcha with old NEXTEL phones is they need to have a SIM card in them that was previously activated on an iDEN network to activate the DirectTalk feature.  The MOTOTALK platform is an ID-based system and each phone or DTR/DLR radio has its own unique 11-digit Private ID, sort of like an Electronic Serial Number (ESN).  In the DTRs and DLRs, this is ID loaded by Motorola at the factory and is not changeable by the end user or with the CPS.  For private talkgroups and private 1 to 1 calling, individual radios only know each other by their 11 digit Private ID.  NEXTEL phones with the DirectTalk feature form the 11-digit Private ID from 1 plus the area code and phone number that was assigned to the phone when it was activated on the network.  This is why an old NEXTEL phone must have a previously activated SIM card in it to enable the DirectTalk feature.
 
DTR/DLR FHSS on 900MHz:

The DTRs and DLRs use a hopset of 50 frequencies spread across the entire 902-928MHz band and spend no more than 90ms on any given freq in the hopset.  The DTRs make about 11 hops per second.  The digital modulation on a given freq in the hopset is according to an 8-level modulation scheme.  The occupied BW on a given freq in the hopset is around 26 kHz.  Motorola's VSELP vocoder is used.  VSELP is what NEXTEL phones used.
 
Per FCC 15.247, an FHSS device operating in the 902-928MHz band must use a minimum of 50 frequencies in the hopset and output power is limited to 1W (+30dBm).  The legacy DTRs were FCC certified at 890mW (+29.5dBm).  The DTR600/700 models were FCC certified at 830 mW (+29.2 dBm).  The DLRs were FCC certified at 880mW (+29.4 dBm).  The few tenths of a dB under the +30dBm legal limit is to account for measurement uncertainty and slight variation in power output from unit to unit and not exceed the 1W (+30dBm) legal limit.  The power numbers in the FCC certs reflect what was measured from the individual sample submitted to the accredited test lab for cert testing.

 
My DTRs:
I own a small fleet of legacy DTR650 radios and a small fleet of DTR700 radios.  The DTR650 has been around since 2006 and was discontinued in November 2018 when the DTR600/700 models were released.  The DTR600 and DTR700 models are the replacement for the legacy DTR 410/550/650 models.  The DTR600/700 programs a little differently from the legacy DTRs but are fully backward compatible.  I have also owned a small fleet of DLR1060 radios which also work with the DTRs.  I later sold my DLRs to a friend for his business as I traded up to the DTR700 and kept my DTR650 fleet.  At first he wasn't sure what he was going to use them for except maybe as rental radios for his customers but now he and his employees use them all the time around the office and at jobsites.
 
The DTRs are my professional quality digital replacement for GMRS/FRS for local on-site simplex type use with family and friends.  I never got them to set any range records but they work amazingly well and are capable of outperforming conventional Part 90/95 UHF portables on simplex.  They totally blow FRS away.  Where they beat other radios is when working inside buildings.  Where they blow all others away is when aboard cruise ships.  People who have used them on cruise ships report having full ship coverage on all decks compared to a pair of 4W UHF commercial portables on GMRS simplex which had trouble penetrating more than about 2 decks.  Like when inside buildings, the ship is much more open at 900MHz compared to 462/467MHz (GMRS/FRS) and VHF MURS.  The ship represents a compartmentalized metal enclosure with many reflections created.  The many reflections inside the ship actually helps at 900MHz and the FHSS operation causes the individual hot spots and dead spots to hop around as the frequency hops.  The FHSS operation effectively stirs the modes so to speak as the frequency hops.
 
A coworker once asked me why not just use FRS?  My answer was that I have already been doing that since FRS was created in 1996 and longer than that as a GMRS licensee (KAE9013) since 1992 and using good quality commercial gear.  I want an all digital solution that is higher quality and more professional than FRS.  The fact that they are completely scanner proof and can be made very secure via private talkgroups and private 1 to 1 calling comes as a bonus.  While technically not encrypted, they can be made very secure.  They are not monitorable on any consumer grade receiver (i.e., scanner) so don't even bother trying.  I have also been bit by the digital radio bug as a ham (N1DAS) and want to use digital radios.  I still have GMRS/FRS and MURS as a backup and for interoperability with non-DTR/DLR users but they are no longer my default go-to modes local on-site simplex use with family and friends.  Aside from occasional light use of FRS with my young nephews when they come to visit, I hardly use GMRS/FRS at all anymore.
 
I love these radios for local on-site simplex type use.  My wife loves using them too when we are out shopping or doing whatever.  She is not a ham but totally gets it when it comes to having radios to stay in touch.  She has told me that she specifically DOES NOT want to use an FRS bubble pack radio.  She much prefers using the DTR radios and wants to use only the good stuff (LOL) when we chitchat on the radio.

I don't care what other people do but absolutely no roger beeps on my radios.  The absolute last thing I would want with my professional quality commercial radios is for them to sound like FRS bubble packs.
I have played around with MDC1200 signaling in Motorola radios and Fleetsync signaling in Kenwood radios.  I haven't used DTMF signaling because it's too d@mn slow.  I put the PTT ID at the start of a transmission, not at the end.   It can be programmed as Pre or Post, or Both.  I like Pre instead of Post because it forces users to wait half a second for the Talk Permit Tone before speaking to allow receiving radios to wake up from battery save mode and allow for CTCSS and/or DCS to decode so the beginning of transmission aren't missed.  I've played around with MDC1200 and Fleetsync signaling but eventually turn them off because they are annoying.  Peace and quiet at the beginning and end of transmissions is a lot nicer.
 

This application appeared today on fccid.io: AZ489FT7146
https://fccid.io/AZ489FT7146
Motorola is adding to their 900MHz FHSS digital on-site business radios with the Curve Series. It is a DLR style radio with 2.4GHz and 5GHz WiFi added to it. I don't understand the "Curve" name to it. Should be interesting. It doesn't appear to have any Bluetooth capability but that might come in a future model. The 900MHz FHSS digital system is compatible with the DTR and DLR series radios.
 

I have been GMRS licensed since December 1992.  My GMRS callsign (KAE9013) resembles an old CB callsign as it predates the FCC Universal Licensing System (ULS).  It also predates the creation of FRS in 1996 and the invasion of the bubble packs which followed.
In 1993, my first GMRS radios was a pair of Motorola GP300 handhelds.  They were expensive at the time but they were the clear quality leader.
Since then I've owned and used the following on GMRS:
Kenwood TK-370 Kenwood TK-370G Kenwood TK-3140 Kenwood TK-3170 Icom IC-F4GT Icom IC-F40GT Motorola HT-1250 Kenwood TK-5310 (still have) Kenwood NX-300 Hytera PD782G Hytera PD362 Hytera X1p (still have) Hytera PD982 (still have) My newest is a Motorola XPR7550e as I'm moving away from Hytera and going full Moto for everything in the future.  No more Kenwood or Icom either.  No cheap Chinese radios (CCRs) since you get the bottom of the barrel cr@p that you pay for.   I'm p!$$ed at Hytera and done with Hytera since the Motorola v. Hytera lawsuit settlement.  I'm also liking Motorola's stuff better anyway.  Only top tier Motorola radios going forward.
 

I see they are on 155MHz.  It is unlikely they are on 155mHz since 155mHz is 0.155Hz.
155.880MHz * 3 = 467.640MHz --> close enough to 467.6375MHz = FRS channel 11.
Any chance the 155.880 transmitter site is VERY close to the OP's location?
 

I would leave them alone and enjoy what you hear.  They could be using DLRs instead of DTRs because they are compatible with the DTRs.  The local Costco Wholesale store near me uses DLR radios and I can hear them on my DTR650 and DTR700 radios when I'm in range. 
The local business you are hearing is 100% legit with their radios.  It's not your problem, so don't make it your problem.  No need to spoil their fun and your ability to listen to them.  They probably don't have a clue and are simply using the radios right out of the box at the factory default settings like FRS bubble packs.  That's how the local Costco store near me seems to operate.
The DLRs will transmit very badly distorted audio if someone shouts into them or talks too close to the mic.  You can tell when DLRs are being used by the badly distorted audio.  The DTR600/700 models have better transmit audio due to automatic gain control (AGC) in the Tx audio path.  The DLRs and legacy DTR410/550/650 models don't have AGC in the transmit audio.  The DTR600/700 models have the best Tx audio, the DLRs have the worst audio, and the legacy DTR410/550/650 models are somewhere in between.  I wish Motorola would update the firmware in the DLRs to add AGC to the transmit audio.
I have custom programming in my DTR fleet and have several private groups set up in them.  I mostly use the private groups.  I purposely keep the factory default programming in them as part of my custom programming to monitor for local activity in my travels and to be able to talk to defaulted DTRs and DLRs if needed.
 

I have been GMRS licensed since December 1992.  My GMRS callsign (KAE9013) resembles an old CB callsign as it predates the FCC Universal Licensing System (ULS).  It also predates the creation of FRS in 1996 and the invasion of the bubble packs which followed.
In 1993, my first GMRS radios was a pair of Motorola GP300 handhelds.  They were expensive at the time but they were the clear quality leader.
Since then I've owned and used the following on GMRS:
Kenwood TK-370 Kenwood TK-370G Kenwood TK-3140 Kenwood TK-3170 Icom IC-F4GT Icom IC-F40GT Motorola HT-1250 Kenwood TK-5310 (still have) Kenwood NX-300 Hytera PD782G Hytera PD362 Hytera X1p (still have) Hytera PD982 (still have) My newest is a Motorola XPR7550e as I'm moving away from Hytera and going full Moto for everything in the future.  No more Kenwood or Icom either.  No cheap Chinese radios (CCRs) since you get the bottom of the barrel cr@p that you pay for.   I'm p!$$ed at Hytera and done with Hytera since the Motorola v. Hytera lawsuit settlement.  I'm also liking Motorola's stuff better anyway.  Only top tier Motorola radios going forward.
 

I don't care what other people do but absolutely no roger beeps on my radios.  The absolute last thing I would want with my professional quality commercial radios is for them to sound like FRS bubble packs.
I have played around with MDC1200 signaling in Motorola radios and Fleetsync signaling in Kenwood radios.  I haven't used DTMF signaling because it's too d@mn slow.  I put the PTT ID at the start of a transmission, not at the end.   It can be programmed as Pre or Post, or Both.  I like Pre instead of Post because it forces users to wait half a second for the Talk Permit Tone before speaking to allow receiving radios to wake up from battery save mode and allow for CTCSS and/or DCS to decode so the beginning of transmission aren't missed.  I've played around with MDC1200 and Fleetsync signaling but eventually turn them off because they are annoying.  Peace and quiet at the beginning and end of transmissions is a lot nicer.
 

LOL, that's me.  I am the one who started that thread on RR.  I have a couple of T800 Talkabouts and the X-Pand in them appears to be a little less aggressive compared to the older Talkabouts.  Motorola probably has tweaked the amount of compression and expansion over the years to make it work better.  The older Talkabouts were manufactured for Motorola by Giant International in China.  The deal with Giant International ended several years ago and the newer T-series Talkabouts are genuine Motorola manufactured in Malaysia.  I noticed the build quality is much better in the newer T-series Talkabouts.
I thought Motorola may have tweaked the companding in them based on past (bad) experiences with the older TalkAbouts.  My wife (g/f at the time) and I had a pair of Motorola Talkabout 250 FRS radios back in the early days of FRS (14 channels).  This was around 1997-1998.  The Talkabout 250 aggressively compressed the Tx audio and aggressively expanded the receive audio.  When hearing audio from other radios that didn't compand their audio, the expander in the Talkabouts totally blew the audio apart to the point that basic functionality as a 2-way radio was seriously impaired.  Even when both Talkabout 250 radios talked to each other and properly compressed the Tx audio and properly expanded the Rx audio, the audio was still BAD.  It was square wave audio between the Talkabouts and hearing expanded audio from non-companded radios was even worse.  It. Was. THAT. Bad.  It is no wonder that Motorola's X-Pand audio companding system is so seriously hated.
The Talkabout FRS radios and Motorola's business radios aka business bubble packs as I like to call them could be cleaned up and made a lot better if Motorola would add the option to disable X-Pand.  Using X-Pand requires ALL radios talking to each other to be using X-Pand in order for all radios to sound right.  Use X-Pand when all radios are using X-Pand and disable X-Pand when one or more radios in a group don't have X-Pand.  If a radio has an audio companding feature, the radio needs to have the ability to enable or disable the feature.  Unfortunately X-Pand is always enabled in the Talkabouts and in Motorola's analog business radios and there is no option to disable X-Pand.
I expected the T600 H2O radios to have X-Pand like the other Talkabouts and was pleasantly surprised to find it is one of a few Talkabout models that don't have X-Pand.  The only newer T-series Talkabouts I have experience with to date are the T800, T600, and T460/465.
T460/465:  Has X-Pand
T800:  Has X-Pand
T600 H2O:  NO X-Pand
 

I've thought of doing this but don't have any LTR capable radios.  It would be set up as a single channel LTR system and with the pulse turned off.  I have heard of exactly this being done to thwart repeater jammers and unauthorized users.
I've thwarted a well known jammer in the past by using DCS/DPL instead of CTCSS/PL.  The jammer in this case had antiquated radios that only had CTCSS/PL capability and no DCS/DPL capability.  He also didn't have a clue about DCS/DPL.  I've heard him screaming on the air about being unable to get into my repeater.  He was continually p!$$ed about not being able to get into the repeater after trying almost every CTCSS/PL tone.  I've heard  of DPL also being referred to as "Definitely Prevents Losers" LOL.  This won't work today with most modern radios having DCS/DPL in addition to CTCSS/PL.
 

I've thought of doing this but don't have any LTR capable radios.  It would be set up as a single channel LTR system and with the pulse turned off.  I have heard of exactly this being done to thwart repeater jammers and unauthorized users.
I've thwarted a well known jammer in the past by using DCS/DPL instead of CTCSS/PL.  The jammer in this case had antiquated radios that only had CTCSS/PL capability and no DCS/DPL capability.  He also didn't have a clue about DCS/DPL.  I've heard him screaming on the air about being unable to get into my repeater.  He was continually p!$$ed about not being able to get into the repeater after trying almost every CTCSS/PL tone.  I've heard  of DPL also being referred to as "Definitely Prevents Losers" LOL.  This won't work today with most modern radios having DCS/DPL in addition to CTCSS/PL.
 

I've thought of doing this but don't have any LTR capable radios.  It would be set up as a single channel LTR system and with the pulse turned off.  I have heard of exactly this being done to thwart repeater jammers and unauthorized users.
I've thwarted a well known jammer in the past by using DCS/DPL instead of CTCSS/PL.  The jammer in this case had antiquated radios that only had CTCSS/PL capability and no DCS/DPL capability.  He also didn't have a clue about DCS/DPL.  I've heard him screaming on the air about being unable to get into my repeater.  He was continually p!$$ed about not being able to get into the repeater after trying almost every CTCSS/PL tone.  I've heard  of DPL also being referred to as "Definitely Prevents Losers" LOL.  This won't work today with most modern radios having DCS/DPL in addition to CTCSS/PL.
 

I would leave them alone and enjoy what you hear.  They could be using DLRs instead of DTRs because they are compatible with the DTRs.  The local Costco Wholesale store near me uses DLR radios and I can hear them on my DTR650 and DTR700 radios when I'm in range. 
The local business you are hearing is 100% legit with their radios.  It's not your problem, so don't make it your problem.  No need to spoil their fun and your ability to listen to them.  They probably don't have a clue and are simply using the radios right out of the box at the factory default settings like FRS bubble packs.  That's how the local Costco store near me seems to operate.
The DLRs will transmit very badly distorted audio if someone shouts into them or talks too close to the mic.  You can tell when DLRs are being used by the badly distorted audio.  The DTR600/700 models have better transmit audio due to automatic gain control (AGC) in the Tx audio path.  The DLRs and legacy DTR410/550/650 models don't have AGC in the transmit audio.  The DTR600/700 models have the best Tx audio, the DLRs have the worst audio, and the legacy DTR410/550/650 models are somewhere in between.  I wish Motorola would update the firmware in the DLRs to add AGC to the transmit audio.
I have custom programming in my DTR fleet and have several private groups set up in them.  I mostly use the private groups.  I purposely keep the factory default programming in them as part of my custom programming to monitor for local activity in my travels and to be able to talk to defaulted DTRs and DLRs if needed.
 

I received my new amateur call sign yesterday. I was able to get my dad's call sign, WB9VLW. The photo is one of his old tags.

I too have noticed an uptick of business use over the past couple of years since the rewrite of the Part 95 rules in 2017.  I'm not complaining since business use of FRS is 100% legal.  We have to coexist as best we can.  Going with the flow of Part 90 by narrowbanding my commercial gear on GMRS solved all of my adjacent channel splatter problems.

No programming is needed to use the DTRs and DLRs with each other right out of the box at the factory default settings.   Customization of features and settings requires the Motorola Business Radio CPS and is a free download from Motorola.  Some features and settings on each model can be changed without requiring the CPS.  The CPS cable is around $35 on Amazon.  The same CPS and cable programs all of Motorola's business radios (RDV/RDU series, RM series, RMM series, etc.).  The one exception is the legacy DTR410/550/650 models use a different CPS cable.  You can download and install the CPS and play around with it and explore the DTR/DLR features and settings.  The latest version of the CPS is R08.02 and programs all of the older models.  You don't need a particular version of the CPS to program an older radio.  Just use the latest CPS version.
 
The Motorola Business Radio CPS can be downloaded from here:
https://www.motorolasolutions.com/en_us/products/two-way-radios/commercial-business-two-way-radio-systems/on-site-business-radios/dtr-series/dtr700.html#tabresource
 
There is no "pairing" of DTRs/DLRs like there is with Bluetooth devices.  They pair up with each other on the fly with each PTT press.  They do have to first be on the same frequency hopset and talkgroup ID in order to work with each other.  A transmitting DTR/DLR listens for an acknowledgement from a receiving DTR/DLR radio during the NEXTEL-like PTT "chirp" talk permit tone to sync up to allow transmission to continue.  When in range, transmission simply continues.  When out of range, transmission stops after the PTT chirp and emits a warning beep indicating the call failed.  The beep is a soft "do-do-doot" sound on the DLRs and DTR600/700.  A DTR600/700 will also display a Call Failed message.  The legacy DTR410/550/650 models will scream at you like an old NEXTEL phone and display a User not Available message.  The end result is you will always know that you are in range and your transmission was heard and acknowledged by another radio.  This makes it easy for range testing because you don't need two people for "Can you hear me now?" testing.  You can leave one radio on the dining room table at home and then take the other radio with you and go for a drive and press PTT to see where you get connect hits.
 
I have found people tend to use these radios right out of the box at the factory default settings, like FRS bubble packs.  I have customized the programming in my DTRs but I purposely kept the factory default public talkgroups in my programming to listen to and talk to defaulted radios.  I have private groups in my programming to keep my DTRs private when I want that.  I have monitored activity on the default public groups in my travels when passing through major retail areas.  The local Costco Wholesale near me uses DLR radios at the factory defaults and I can hear them when I'm in range.
 
They are amazing radios.

I have played around with the companding option in my commercial radios I use on GMRS.  I end up turning the compander off after a while because of the issues it causes.  The companding feature does work as advertised to help clean up the audio SNR.  The companded audio has a "processed" quality to it and I don't mind that.  The problem is it requires ALL radios talking to each other to also be using companding in order to sound right.  It's an all or nothing type deal.  Radios that don't compress their transmitted audio will sound muffled and distorted when heard out of companded radios.  The expander in the receiver expands audio that wasn't compressed originally and blows it apart and sounds like 'expletive'.  The compander is best left disabled when you have a mix of radios that do and don't compand their audio.  Motorola includes a low level expander (LLE) option in their top tier radios.  When using LLE, the transmit audio is not compressed, only the received audio is expanded by a small amount.  It gives the audio a very slightly "fuzzy" quality to it under some conditions.   Overall if a radio has companding capability, the radio needs to include the option to disable the compander.  The compander feature should be OFF by default.
 
The Motorola Talkabout FRS bubble packs use companding.  Motorola calls this feature "X-Pand".  The compander is always enabled and with no option to disable it.  With Motorola's VHF and UHF business radios, the Business Bubble Packs as I like to call them also compand audio on narrow bandwidth channels with no option to disable the compander.  People who have complained about bad receive audio quality out of the Motorola Talkabout FRS bubble packs are really complaining about the effects of the compander on the received audio, especially when hearing radios that don't compress their transmit audio because they don't have companding.  Motorola could greatly improve the Talkabout FRS bubble packs by simply adding the option to disable the compander.
 
My wife (g/f at the time) and I had a pair of Motorola Talkabout 250 FRS bubble packs in the early days of FRS.  The Talkabout 250 was one of the early 14-channel FRS bubble packs from Motorola.  It was one of the first models to push their "X-Pand" audio companding feature.  Motorola added X-Pand to all of their analog radios back then.  Motorola's top tier radios have the ability to enable or disable companding on a per channel basis.  With Motorola's FRS bubble packs and their business bubble packs, the compander is always enabled.  The Talkabout 250 had LOUD audio for hearing them in noisy environments which I liked but the companded audio sounded like 'expletive'.  The radios aggressively companded the audio by over-compressing the transmitted audio and over-expanding the received audio.  The companded audio quality was so bad and to the point that basic functionality of the radio was impaired.  The radio was almost unusable with radios that don't compand their audio.  It was THAT bad.  Reducing the expansion ratio in the expander part of the companding system would have helped a lot.
 
Wikipedia article on companding:
https://en.wikipedia.org/wiki/Companding

I have played around with the companding option in my commercial radios I use on GMRS.  I end up turning the compander off after a while because of the issues it causes.  The companding feature does work as advertised to help clean up the audio SNR.  The companded audio has a "processed" quality to it and I don't mind that.  The problem is it requires ALL radios talking to each other to also be using companding in order to sound right.  It's an all or nothing type deal.  Radios that don't compress their transmitted audio will sound muffled and distorted when heard out of companded radios.  The expander in the receiver expands audio that wasn't compressed originally and blows it apart and sounds like 'expletive'.  The compander is best left disabled when you have a mix of radios that do and don't compand their audio.  Motorola includes a low level expander (LLE) option in their top tier radios.  When using LLE, the transmit audio is not compressed, only the received audio is expanded by a small amount.  It gives the audio a very slightly "fuzzy" quality to it under some conditions.   Overall if a radio has companding capability, the radio needs to include the option to disable the compander.  The compander feature should be OFF by default.
 
The Motorola Talkabout FRS bubble packs use companding.  Motorola calls this feature "X-Pand".  The compander is always enabled and with no option to disable it.  With Motorola's VHF and UHF business radios, the Business Bubble Packs as I like to call them also compand audio on narrow bandwidth channels with no option to disable the compander.  People who have complained about bad receive audio quality out of the Motorola Talkabout FRS bubble packs are really complaining about the effects of the compander on the received audio, especially when hearing radios that don't compress their transmit audio because they don't have companding.  Motorola could greatly improve the Talkabout FRS bubble packs by simply adding the option to disable the compander.
 
My wife (g/f at the time) and I had a pair of Motorola Talkabout 250 FRS bubble packs in the early days of FRS.  The Talkabout 250 was one of the early 14-channel FRS bubble packs from Motorola.  It was one of the first models to push their "X-Pand" audio companding feature.  Motorola added X-Pand to all of their analog radios back then.  Motorola's top tier radios have the ability to enable or disable companding on a per channel basis.  With Motorola's FRS bubble packs and their business bubble packs, the compander is always enabled.  The Talkabout 250 had LOUD audio for hearing them in noisy environments which I liked but the companded audio sounded like 'expletive'.  The radios aggressively companded the audio by over-compressing the transmitted audio and over-expanding the received audio.  The companded audio quality was so bad and to the point that basic functionality of the radio was impaired.  The radio was almost unusable with radios that don't compand their audio.  It was THAT bad.  Reducing the expansion ratio in the expander part of the companding system would have helped a lot.
 
Wikipedia article on companding:
https://en.wikipedia.org/wiki/Companding

I have played around with the companding option in my commercial radios I use on GMRS.  I end up turning the compander off after a while because of the issues it causes.  The companding feature does work as advertised to help clean up the audio SNR.  The companded audio has a "processed" quality to it and I don't mind that.  The problem is it requires ALL radios talking to each other to also be using companding in order to sound right.  It's an all or nothing type deal.  Radios that don't compress their transmitted audio will sound muffled and distorted when heard out of companded radios.  The expander in the receiver expands audio that wasn't compressed originally and blows it apart and sounds like 'expletive'.  The compander is best left disabled when you have a mix of radios that do and don't compand their audio.  Motorola includes a low level expander (LLE) option in their top tier radios.  When using LLE, the transmit audio is not compressed, only the received audio is expanded by a small amount.  It gives the audio a very slightly "fuzzy" quality to it under some conditions.   Overall if a radio has companding capability, the radio needs to include the option to disable the compander.  The compander feature should be OFF by default.
 
The Motorola Talkabout FRS bubble packs use companding.  Motorola calls this feature "X-Pand".  The compander is always enabled and with no option to disable it.  With Motorola's VHF and UHF business radios, the Business Bubble Packs as I like to call them also compand audio on narrow bandwidth channels with no option to disable the compander.  People who have complained about bad receive audio quality out of the Motorola Talkabout FRS bubble packs are really complaining about the effects of the compander on the received audio, especially when hearing radios that don't compress their transmit audio because they don't have companding.  Motorola could greatly improve the Talkabout FRS bubble packs by simply adding the option to disable the compander.
 
My wife (g/f at the time) and I had a pair of Motorola Talkabout 250 FRS bubble packs in the early days of FRS.  The Talkabout 250 was one of the early 14-channel FRS bubble packs from Motorola.  It was one of the first models to push their "X-Pand" audio companding feature.  Motorola added X-Pand to all of their analog radios back then.  Motorola's top tier radios have the ability to enable or disable companding on a per channel basis.  With Motorola's FRS bubble packs and their business bubble packs, the compander is always enabled.  The Talkabout 250 had LOUD audio for hearing them in noisy environments which I liked but the companded audio sounded like 'expletive'.  The radios aggressively companded the audio by over-compressing the transmitted audio and over-expanding the received audio.  The companded audio quality was so bad and to the point that basic functionality of the radio was impaired.  The radio was almost unusable with radios that don't compand their audio.  It was THAT bad.  Reducing the expansion ratio in the expander part of the companding system would have helped a lot.
 
Wikipedia article on companding:
https://en.wikipedia.org/wiki/Companding

It IS interesting and I don't know if it repeats on the same frequency hopset or not.  I don't know the details of how it works.  It would be interesting and cool to try but I don't feel like spending the $,$$$$.$$ for a DRX.
 
I think the cable that comes with the DRX for connecting the two units together is 10 ft or 20 ft long.  There is an optional 50 ft cable for it to get the two units further apart.
 
The current DRX based on a pair of DLRs is a refresh of their older DRX unit which was based on a pair of legacy DTRs and with the same price tag. The legacy DTR410/550/650 models were discontinued in November 2018 when the DTR600/700 models were released.  Cane Wireless needed to develop a DLR based DRX going forward.  The DRX also needs to work with the Profile ID mode channels which the legacy DTRs can't do because they don't have the 4 digit PIN feature.
 
From what I read about the DRX is that the digital audio delay between radios approximately doubles when talking through the DRX.  Multiple DRXs on the same channel can be used to further extend coverage on a channel but Cane Wireless recommends against it because the audio delay increases and audio quality may decrease.  This makes me wonder if analog audio passes between the two units making up a DRX repeater.  The audio quality would decrease due to effects of double vocoding, etc.

That's something I had lingering in my mind after reading your links and studying DTR/DLR thing. I'll leave hacking for some time later.
 
The first thing (ok, second) is of course, to plug in simplex repeater and bring the whole contraption high up on a makeshift mast. That's could be a lot of fun, I already see it.

Thanks.  I just made a few minor edits.  Maybe the next thing for me to do is write up a DTR/DLR programming overview and explain a lot of the workings.
 
Programming the DTRs and DLRs is often cryptic and befuddling to new users.  No programming is needed to use DTRs and DLRs right out of the box at the factory default settings.  Customization of features and settings requires the CPS.  Some settings can be changed without requiring the CPS.  Programming the legacy DTR410/550/650 is cryptic and the DLR programming cleaned up a lot of things and made it a little less cryptic.  The DTR600/700 models program like the DLRs.  I suspect the DTR600/700 models use the DLR's code base.  I am not surprised Motorola adopted the DLR way of programming going forward.
 
The DTR600/700 models are backward compatible with the legacy DTRs but it requires some understanding of the differences.  When I owned DTR650s, DLR1060s, and DTR700s, I had them all working with each other on public and private talkgroups.  The DLRs and DTR700s added a 4 digit Profile ID Number (PIN) feature which the legacy DTRs don't have.  I had my DLRs and DTR700s working with each other on Profile ID mode channels.  The PIN feature allows you to take DLRs right out the box and set a 4 digit PIN to secure all channels in them without requiring the CPS.  With the legacy DTRs, the only way to secure them was to use the CPS to program private talkgroups into them.  Motorola made it insanely easy for DLR users and DTR600/700 users to secure their channels in radios right out of the box without needing the CPS.
 
A lot can be learned about them by downloading and installing the CPS and exploring the DTR and DLR programming.  The CPS has default DTR and DLR templates to work from so you don't need to read a radio first to use the CPS and play around with the programming.  The latest CPS version is R08.02 and programs all of the older models too.  You don't need an older version of the CPS to program an older radio.  Just use the latest version of the CPS.

David, thank you very much for the very comprehensive deep dive into DTR-DLR world. I will wait for my newly bought DLRs to come before asking more questions.

I actually bought a pair of DLR1060 on ebay today. Going to compare performance with GMRS handhelds and mobiles. The usage mode is outdoors: camping, hikes, mountains, woods. It is not very clear to me how 900MHz at 1W with spread-spectrum and error correction would perform against ole wide-band FM at 4W (and at 40W). Of course, the moment I bought DLRs, the cheap chargers disappeared from ebay. But I'm not in rush, will wait for something below $30.
 
So, what you, David, are saying, is that the older DTRs do not have this 4-digit ID, mentioned in DLR manual. And to make the old DTR work with new DLR is to program talk groups into DLR. The programming the 4-digit ID into old DTR will not work because there is no 4-digit ID. Right? Wrong? I order to introduce the older DTR into the network of DLRs I will need to delete the 4-digit ID in DLRs and program the talkgroups, is this correct?
At this moment of time my interest is purely academical because I do not have old DTR, and DLRs are not here with me yet.