Locator Mode; Telephone Line Interface - Panasonic KX-TG2343F Service Manual

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15.5. Locator Mode

1. Press the base LOCATOR button, then a beep is output from pins 29 and 31 of IC501, and blinks on the display [IN USE] (LED)

is caused by IC501.

2. At the same time, a beep is output from pin 29, pin 31 of IC501.

Telephone Line Interface Circuit:

Function

• • • • Bell signal detection

• • • • ON/OFF hook and pulse dial circuit

• • • • Side tone circuit

Bell signal detection and OFF HOOK circuit:

In the idle mode, Q104 is open to cut the DC loop current and decrease the ring load. When ring voltage appears at the Tip (T)

and Ring (R) leads (When the telephone rings), the AC ring voltage is transferred as follows:

T → L101 → R130 → C116 → Q106 → DSP pin 3. [BELL]

When the CPU (DSP) detects a ring signal, Q104 turns on, thus providing an off-hook condition (active DC current flow through

the circuit). Following signal flow is the DC current flow.

T → L101 → D101 → Q104 → Q161 → R164 → D161 → D101 → L102 → P101 → R

ON HOOK Circuit:

Q104 is open, Q104 is connected as to cut the DC loop current and to cut the voice signal. The unit is consequently in an on-

hook condition.

Pulse Dial Circuit:

DSP pin 4 turns Q104 ON/OFF to make the pulse dialing.

Side Tone Circuit:

Basically this circuit prevents the TX signal from feeding back to RX signal.As for this unit, TX signal feed back from Q161 is

canceled by the chancellor circuit of DSP.

KX-TG2343F / KX-TG2343P / KX-TG2343W / KX-TGA233F / KX-TGA233P / KX-TGA233W

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