User Manual Part 1

CIRCUIT ANALYSIS
52 MM101271V1 R2A
Quad RS422 receiver U26 converts and buffers signals coming from the Simulcast cross
connect panel going to the SitePro controller Board. These signals are:
• 150 Hz + (IN)
• 150 Hz - (IN)
• 9.6 DATA + (IN)
• 9.6 DATA - (IN)
• 9.6 REF + (IN)
• 9.6 REF - (IN)
• EXT 150 Hz + (OUT)
• EXT 9.6 DATA + (OUT)
• EXT 9.6 REF + (OUT)
Audio Switching
The audio bypass circuit consisting of relay driver U27 and relays K1 and K2 allows the
audio to be interrupted and receive voice to be sent back to the station, when in the
bypass mode.
In normal Simulcast operation Rx AUDIO L connects through relay K1 to RXV R. TX
AUDIO L connects though K1 to TXV R. Also, RX AUDIO H connects through relay
K2 to RXV T. TX AUDIO H connects through K2 to TXV T.
When the BYPASS signal goes low, forward biasing diode D15, relay drivers U27 cause
relays K1 and K2 to activate. This action places the Simulcast System in the Bypass
mode. RX AUDIO L now connects through K1 to TX AUDIO L. Likewise, RX AUDIO
H connects through K2 to TX AUDIO H, returning the audio back to the station.