13.3. Auto Disconnect Circuit
Function:
This circuit is used to detect the fact that another telephone connected to the same line is OFF-
HOOK while the unit is in a receiving status or OGM transmitting status.
Circuit Operation:
The voltage pin 40 of IC501 is monitored. If a parallel-connected telephone is put into an OFF
HOOK status, the presence/absence of a parallel connection is determined when the voltage
changes by 0.2V or more.
When the set detects the parallel-connected telephone is OFF HOOK status, the line is
disconnected.
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