Ncu Section - Panasonic KX-MB771GR Service Manual

6.4.

NCU SECTION

6.4.1. GENERAL
This section is the interface between the telephone line and external telephone. It is composed of an EXT. TEL line relay (RLY100),
bell detection circuit, TAM interface circuit and line amplifier.
6.4.2. EXT. TEL. LINE RELAY (RY100)
1. Circuit Operation
Normally, this relay switches to the external telephone side and switches to the open side while OFF-HOOK.
IC300 (U25) High Level→Q100 ON→RY100 (ON)
6.4.3. BELL DETECTION CIRCUIT
1. Circuit Operation
The signal waveform is indicated below. The bell signal input to IC101 and ring detected signal output from pin 16 of IC100.
IC300 monitor this signal and judged as bell.
TEL LINE→IC101 (8,9 - 5,6)→IC100 (9,10 - 16)→IC300(L23)
6.4.4. 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 sub-
scribe 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 1200 Hz sine wave, and data 1 a 2200 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 mes-
sage 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 Soc (IC300).
TEL LINE→IC101 (8,9 - 5,6)→IC100 (9,10 - 5)→IC300(AD26)
6.4.5. REMOTE FAX ACTIVATION CIRCUIT
1. Function
Another telephone connected to same line activates the unit to the FAX mode by using a DTMF signal.
2. Signal Path
TEL LINE→IC101 (8,9 - 5,6)→IC100 (9,10 - 5)→IC300(AD26)
6.4.6. TAM INTERFACE CIRCUIT
This circuit is to switch between FAX receiving and the external TAM's message recording automatically.
For details, please refer to TAM INTERFACE SECTION (P.28).
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KX-MB771GR