Its (Integrated Telephone System) And Monitor Section; Ext. Tel - Panasonic KX-FT72BR-G Service Manual

5.9.

ITS (Integrated telephone System) and MONITOR SECTION

5.9.1. GENERAL
During the monitor operation, the speaker output passes through the power amplifier (IC1) [Analog board].
The DTMF signal is output from the modem (IC1: digital board). The alarm tone, the key tone, bell tone, and beep are output from
gate array IC1 (digital board). During a pulse dial operation, the monitor tone is output from gate array IC1.
5.9.2. MONITOR CIRCUIT
1. Function
This is the function when you are not holding the handset and can hear the caller´s voice from the line.
2. Circuit Operation
(Monitor Signal Path)
Signals received from the telephone line are output through at the speaker via the following path.
Refer to CHECK SHEET (P.65)
5.9.3. HANDSET CIRCUIT
1. Transmission signal
Refer to 2.3.4.4. Analog Board Section
2. Reception Signal
Refer to CHECK SHEET (P.65)
5.9.4. MONITOR CIRCUIT
1. DTMF Monitor
(Monitor)
Refer to CHECK SHEET (P.65)
(Handset)
2. Alarm/Beep/Key tone/Bell
Refer to CHECK SHEET (P.65)
3. Dummy Ring Back Tone
Same with the modem signal transmission.

5.10. EXT. TEL

EXT. TEL JACK is provided for the external TEL connection.
Connect the telephone to the EXT. TEL JACK. Because the unit has the priority, EXT. TEL is disconnected when the unit is OFF-
HOOK.
1. EXT. TEL DC LOOP
(Signal Path)
T → CN4(3) → POS1 → L2 → RL1(3-5) → L3→CN5(4)→EXT.TEL → CN5(3)→L4 → R14 →L1→CN4(4)→ R
2. REMOTE RECEIVING
This is the parallel connection DTMF signal for the TEL or EXT. TEL mode between T and R. When the other party is a FAX,
the unit changes to FAX receiving.
(Signal path)
Refer to CHECK SHEET (P.65)
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KX-FT72BR-G