If the AM-1780 relays click, the CX-4723 is bad.
repair the CX-4723.
If the relays in the AM-1780 do not click, the AM-1780 is bad.
Send to IDS for repair.
11. NO SIDETONE.
a. Situation 4. When performing EPC step 2a, the symptom (no sidetone)
is observed (Figure 39). This indicates the intercom talk/listen circuit is
bad. This symptom is caused by either a short or an open.
A short anywhere on the talk/listen circuit will cause NO SIDETONE
at all control boxes; an open will affect only the control box being