Panasonic UF-5500, Service Manual

Page: 36 / 365

36
UF-5500 / 4500
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 (RLY100)
1. Circuit Operation
Normally, this relay switches to the external telephone side and switches to the open side while OFF-HOOK.
IC300 (R33) High Level
→
Q100 ON
→
RLY100 (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 15 of IC100.
IC300 monitor this signal and judged as bell.
TEL LINE
→
IC101 (8,9 - 5,6)
→
IC100 (9,10 - 15)
→
IC300(AA25)
6.4.4. 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)
6.4.5. 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.37).
㪊㪅㪊㪭
IC100 (15) IC300 (AA25)
Between the Tip and Ring
from the telephone line
48V
about 150V