Line Monitor Circuit - Panasonic UF-580 Service Manual

6.2.5

Line Monitor Circuit

The Line Monitor Circuit consists of an operational DAA (The secondary side chip) and its peripheral
circuits. Its function is to monitor the dial tone, DTMF tone, response signals, etc. over the speaker. It also
sounds the output of the key touch tones, alarm tones, etc. from the panel CPU over the speaker. The
Received Signals are output from DAA of Secondary circuit, and through Analog AGC, Electronic Volume,
Amplifier and over the speaker.
The monitor tone from the phone line and the buzzer tone from the panel can be adjusted from the Control
Panel.
Volume
Line Monitor Signal
Control
-
(from AGC Circuit)
Circuit
Speaker
(IC20, 2) Amplifier
(IC21)
(Q4,5)
+
Buzzer Clock
Speaker
(from Control Panel Unit)
AGD
(+2.5VDC)
Level Control
Buzzer Tone Switch
Circuit
(from Output Port)
(Q3)
Line Monitor Circuit
Block Diagram
205