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Current supply circuit / (c) Hook detection circuit / (d) 2-4 lines
conversion circuit / (e) A/D and D/A conversion circuit (CODEC)
IC118 /
Circuit Operation: / (a) Circuit for detection whether the Door-
Phone is connected or not. / When the Door-Phone is not
connected, base of Q105 is high. When corrector of Q105 is low,
input pin of G/A (IC101) is low. When the Door-Phone is
connected, base of Q105 is low. When corrector of Q105 is high,
input pin of G/A (IC101) is high. CPU(IC100) on 1AP gets
information through IC101 whether the Door-Phone is connected
or not. /
(b) Current Supply Circuit / Q106 supplies current to the Door-
Phone line through the transformer (T10). /
(c) Hook Detection Circuit / When the call button of Door-Phone
isn't pushed, base of Q110 is high. When corrector of Q110 is low,
input pin of G/A(IC101) is low. When the call button of Door-Phone
is pushed, base of Q110 is low. When corrector of Q110 is high,
input pin of IC101 is high. CPU(IC100) on 1AP gets information
through IC101 whether the call button is pushed or not. /
(d) 2-4 Lines Conversion Circuit / This circuit converts 2-line
analogue signals to 4-line signals. /
(e) A/D, D/A Conversion Circuit / This circuit is for converting the
analogue signals from Door-Phone to the PCM digital signals to
present to the PCM highway, and also converting the data on the
PCM highway into the analogue signals to the Door-Phone. This
circuit has the power down function and the u/A conversion
function. /
/ / / / / / / / / / /
6. Door Opener Circuit
This is the relay circuit which controls the Door Opener
19
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