Phonak DigiMaster X Installation Instructions Manual page 4

Connection to computer (recording) and amplification system
Mic input = 3.5 mm mono jack
Y-jack splitter
Mic input = 3.5 mm
Caution: such connections may cause hum.
Connection to Grommes-Precision XAV-102-A
The gain of the microphone input is set by a potentiometer on the Wall Plate
Remote Module. Precautions should be taken to prevent gain changes.
Rear View
24VAC. Ground.