c. Intercom listen circuit.
The intercom listen circuit starts at the
output of the A250 (Figure 12).
These signals are applied to contacts 20,
11, 14, and 17 of K501; and from
these contacts the audio is applied to pin
L of jacks J504, J505, J506, and
J507 of the AM-1780. (Trace this circuit
on your system diagram.)
Intercom voice signal applied to intercom listen circuit.
(1) When K501 is energized, its contacts close and the listening
circuits to J504, J505, J506, and J507 are completed as shown in Figure 13.
(Trace this circuit on your system diagram.)
Listening circuits completed through K501 to
J504, J505, J506, and J507.