Panasonic KX-FC971CX-S Service Manual page 161

8.7.5. LINE AMPLIFIER AND SIDE TONE CIRCUIT
1. Circuit Operation
The reception signal output from the line transformer T101 is input to pin (2) of IC101 via C129, R115 and then the signal is
amplified at pin (1) of IC101 and sent to the reception system at through the LPF.
8.7.6. Calling Line Identification Circuit
1. Function
This unit is compatible with the Caller ID service offered by your local telephone company. To use this feature, you must
subscribe to a Caller ID service. 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 which is modulated in an FSK
(Frequency Shift Keying) format. Data "0" is a 1300 Hz sine wave, and data 1 a 2100 Hz sine wave.
There are two type of the message format which can be received:i.e.the single data message format and multiple data message
format.
The multiple data format allows to transmit the name and data code information in addition to the time and telephone number
data.
When there is multiple data in the unit, the name or telephone number are displayed.
2. Circuit Operation:
The caller ID signal input from TEL LINE is processed with MODEM (IC505).
Refer to Check Sheet for Signal Route (P.99) for the route of caller ID signal.
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KX-FC971CX-S / KX-FGA521CX-S