Panasonic KX-TA1232 Service Manual page 35

Composition:
CODEC IC (IC7, 8)
IC12, T4, T5, etc.
Circuit Operation:
The hold tone circuit is a circuit which presents the hold tone for the system. The tone sources
are one system of the internal hold tone (as a local option) and two systems of the external hold
tone. The internal hold tone and one of the external hold tone are switchable alternatively to be
used (as a local option). The analog signals from the tone sources are changed to the digital
ones by CODEC IC (IC6) and presented to HWR0 of the up highway. The external hold tone circuit
has AGC function.
External Paging Circuit
Composition:
CODEC IC (IC7, 8)
IC10, T2, T3, etc.
Circuit Operation:
External Paging Circuit is a circuit which presents the voice to the external amplifier. This circuit
converts the digital voice data on the HWS0 of the down highway to the analog signals by
CODEC, and presents the external paging port. This circuit consists of two systems.
Back Up Circuit
Composition:
BAT, C1 etc.
Back Up Circuit is a circuit which has two functions as follows;
- Back up the CPU (IC1) peripherals for one second when AC power
momentarily fails.
- Back up the Clock IC (IC26) and the part of RAM for 7 years.
Circuit Operation:
Back-up is done by the super capacitor (C1) at the momentary AC power failure, and the clock IC
and RAM are backed up by the lithium of secondary battery (BAT).
35