Panasonic KX-TDA6178 Service Manual page 14

24-port single line telephone extension card with caller id
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KX-TDA6178
5.2.12. Power Failure Switch Feature
4 out of 24 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.
5.2.13. Bell Signal Generator and Transmission
In ringing mode, the ringing DC offset and the ringing signal are summed digitally within CODEC in accordance with the pro-
grammed values.
This signal is then converted to an analog signal and applies to the SLIC.
The SLIC amplifies the signal and supplies the line with 75 Vrms.
The bell signal is generated with +80V(VHR) and -55V(VBATH) supplied to SLIC.
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