Read Panasonic KX-TDA0177XJ / KX-TDA0177X (serv.man2) Service Manual online
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KX-TDA0177XJ / KX-TDA0177X
5.2.12. Power Failure Switch Feature
4 out of 16 lines have switching relays (RL200A-D) installed in order to enable the outside call during a power failure. The line con-
nected to the outside call card will be directly connected to the CN201/202 located in forward part of the board via a 4-conductor
TEL cord. In the normal operation mode, it breaks the power failure switching relay, and during a power failure, it makes the power
failure switching relay to initiate Power failure direct connection mode.
nected to the outside call card will be directly connected to the CN201/202 located in forward part of the board via a 4-conductor
TEL cord. In the normal operation mode, it breaks the power failure switching relay, and during a power failure, it makes the power
failure switching relay to initiate Power failure direct connection mode.
5.2.13. Bell Signal Generator
Bell signal for ringing an SLT is generated by amplifying the 20 or 25Hz square wave provided from MPR card to AC75Vrms
onboard. The SW power supply in the BELL circuit generates between +160V and -100V of voltage by switching the +40V from the
power source at 125KHz frequencies. The Bell signal picks up the square wave provided from MPR via a photocoupler, and it is
transformed into SIN wave, then amplified to AC75Vrm bell signal by the amplitude between +160V and -100V of voltage (Mainly
+30Vdc) produced by SW power supply.
When the Bell signal is not needed, bell signal voltage generating circuit can be turned off by transmitting H signal from P21 port
(BELL CNT) of ASIC to reduce the power consumption.
onboard. The SW power supply in the BELL circuit generates between +160V and -100V of voltage by switching the +40V from the
power source at 125KHz frequencies. The Bell signal picks up the square wave provided from MPR via a photocoupler, and it is
transformed into SIN wave, then amplified to AC75Vrm bell signal by the amplitude between +160V and -100V of voltage (Mainly
+30Vdc) produced by SW power supply.
When the Bell signal is not needed, bell signal voltage generating circuit can be turned off by transmitting H signal from P21 port
(BELL CNT) of ASIC to reduce the power consumption.
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