Codan NGT 2010 RF Technical & Service Manual page 778

4-wire interface
Drawing
Four lines may be connected on the 4-wire interface. Line 1 is always connected, lines 2,
3 and 4 are optional. The receive audio for line 1 is applied to connector P3 pins 5 and 6
located on the Backplane PCB, and then via an interface cable to the 4-wire interface
assembly. Lines 2, 3 and 4 use connectors P4, P102, and P103 respectively.
The 4-wire interface consists of two isolating transformers (providing separate Tx and
Rx paths) and includes RF filter capacitors. The output of the Rx transformer connects
via an interface cable to the Tcvr Control connector mounted on the rear of the 8571.
NGT Transceiver System Technical Service Manual
04-02691
8571—Technical description
339