QUANZHOUBAOJIE ELECTRONICS CO.,LTD. Model:BJ-9900
Version:BJ-9900-0812-V1 Page 6 of 75
other signal except the useful and then transmit to ceramic discriminator CD1001 via
the IF amplifier in IC1047.The ceramic discriminator will remove any Variance in
Amplitude in 450KHz IF signal before voice detecting .The ceramic discriminator will
remove any Variance in Amplitude in 450KHz IF signal before voice detecting .
Demodulated sub-band audio restore the network and audio switch D1048 through
signal, and then handle by audio processor IC IC1043.And the filtered audio signal
transmit to audio switch IC1066 and IC1067.
When the built-in speaker is selected, the audio signal will be amplified by IC1069
and then be provided to the built-in speaker.When the external speaker is selected, the
audio signal will be amplified by IC1068 and then transmit through the external speaker
jack to the external speaker.
Squelch control
Main band
when there is not receivable carrier signal in main band , the output nosies for the
IC1044 detector will be amplified while the band pass will be filtered by the IC1044''s
noises amplified part. The generated direct voltage will be transferred to of Main CPU
IC1104 pin31 which will compare the squelch standard level with the settable squelch
level in the front panel which can setted through SQL key.
when there is no receivable carrier signal in main band , The pin76 in IC110 will keep
in LOW position to forbidden the audio output of the speaker.
