User's Manual

TDFM-136B Installation Instructions 08RE398
2.7 Wiring Instructions
Figure 2-3 shows all required connections and recommended wire sizes for the TDFM-
136B Transceiver operation in the airframe.
2.7.1 Main Power +28VDC
The main power +28VDC (±15%) is connected to pins 7 and 14 of the transceiver. Both
pins should be connected.
2.7.2 Main Ground
Ground connections for the transceiver are made on pins 8 and 15. Both pins should be connected
2.7.3 PTT (Ground Keying)
The PTT line is connected to pin 13 and should be floating when the transceiver is in receive mode,
and grounded during transmit mode.
2.7.4 Front Panel Back Lighting
Front panel back lighting connection should be made on pin 3 of the transceiver. The opposite end
of this lead should be connected to the panel lighting system of the aircraft. Before connecting, verify
the required panel lighting voltage, the unit is compatible with both 28V and 5V lighting bus voltages.
2.7.5 Audio Outputs (600 ohms and 4 0hms)
The audio output from pin 9 can be used to drive a 4 ohm speaker up to 2.5 watts. Audio output
from pin 1 is 600 ohms, 0.5 watts maximum.
2.7.6 Audio Output Ground
Pin 10 is the ground for both the 4 ohm and 600 ohm audio output signals on pins 9 and 1.
2.7.7 Mic Signal Input
The microphone input signal is to be provided on pin 6, utilising shielded wire with the shield
grounded to pin 10.
2.7.8 Memory Up/Memory Down
Remote scrolling through the memory positions can be achieved by providing a ground to pins 4 (up)
and 5 (down) through a momentary contact cyclic switch.
2.7.9 Data Input/Output
Channel data may be transferred to and from the unit using RS-232 communications protocol via
pins 2 and 11.
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