Panasonic KX-TA1232 Service Manual page 36

Voltage Watching Circuit
Composition:
Reset IC (IC13)
Q6, 7 etc.
Circuit Operation:
Voltage Watching Circuit is a security circuit which detects the ration of +5 V and +15 V. If +5 V is
derated, this circuit resets the system. If +15 V is derated, this circuit presents "L" to I/O port in
CPU. The ration of +15 V means AC power off.
RS-232C Interface Circuit
Composition:
Receiver/Driver IC (IC15, 16)
16 bit CPU (IC1)
Circuit Operation:
RS-232C Circuit is a circuit for realizing the data transmission between CPU 68301 (IC1) and a
personal computer/printer etc. This circuit consists of a serial interface built in CPU and the level
conversion circuit. When the power turns on, the power supply for the RS-232C driver (IC15, 16)
is controlled by CPU to prevent the indefinite data presentation.
(3) BASIC CO BOARD
BASIC CO BOARD consists of the following:
Call interface
Parallel I/O Circuit
Timing Signal Generation Circuit
Call Interface Circuit
Call Interface Circuit is a circuit which works as the interface between the call line and the PCM
highway, and is classifies as following circuits.
Composition:
(a) Bell Signal Detection Circuit
(b) DC loop formation Circuit
36