Audio-Logic Board connections for MDC Pigtail:

YELLOW--PIN 12 U301 TX AUDIO (MDC MODEM VOLUME @47)
BROWN--PIN 4 OF BELT, PTT
GRAY---- PIN13 OF BELT, DETECTOR AUDIO
BLACK---GROUND
ORANGE--PIN 1 U-303       COS >7 VDC W/SIGNAL, <.5 VDC NO SIGNAL