Panasonic KX-TG2226B Service Manual page 59

Note:
DSP is IC201.
See CPU DATA (BASE UNIT)
You can enable or disable the Auto Disconnect function.
See Check Record ().
17.8. Parallel Connection Detect Circuit
Function:
In order to disable call waiting and stutter tone functions when using telephones connected in
parallel, it is necessary to have a circuit that judges whether a telephone connected in parallel is
in use or not. This circuit determines whether the telephone connected in parallel is on hook or
off hook by detecting changes in the T/R voltage.
It is like an "Auto Disconnect Circuit".
Circuit Operation:
Parallel connection detection when on hook:
When the set is on hook, the voltage is monitored at DSP (DCIN0). There is no parallel connection
if the voltage is 2.50 V or higher, while a parallel connection is deemed to exist if the voltage is
lower.
Parallel connection detection when off hook:
When the set is off hook, the voltage is monitored at DSP (DCIN1); the presence/absence of a
parallel connection is determined when the voltage changes by 0.2 V or more.
17.9. Calling Line Identification (Caller ID)/Call Waiting Caller ID
Function:
Caller ID
The caller ID is a chargeable ID which the user of a telephone circuit obtains by entering a
contract with the telephone company to utilize a caller ID service. For this reason, the operation
of this circuit assumes that a caller ID service contract has been entered for the circuit being
used.
The data for the caller ID from the telephone exchange is sent during the interval between the
first and second rings of the bell signal. The data from the telephone exchange is a modem signal
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