I seem to recall that T1504 was a four bandpass/reject cavity duplex filter. It may have been sold as a kit of parts. But in any event depending upon the frequency band you got a set of critical length interconnect cables and a "T" connector. The duplexer is band pass with reject notch filters. The band pass is wider than the reject notch so after first tuning band pass, then tuning reject, you could fine tune the reject with the pass knobs. That is how I did it and they worked well. The trick was that the screws on the slotted reject loop had to be almost tight so they made reliable connection and then I would "rap" the screws one direction or the other in the slot to tune the notch. A couple Excelite nut drivers were the ideal tools to move the knurled nut. Use one as a "hammer" and the other as a "chisel" and tap their plastic heads together to move the nut just enough. Then hand tighten,
