What fault might cause a station to hear no voice but still hear a call signal?

• A. A faulty transmitter path or microphone; the call path may still be functioning.
• B. A shorted speaker coil.
• C. A loose headset jack.
• D. A faulty power supply.

Answer: (C)

In sound-powered telephones, the voice path and the signaling (call) path can use separate contacts or even separate wiring inside the headset connection. If the headset jack is loose, the microphone contact or the voice path can lose proper connection, so you don’t hear or transmit voice. But the call signal path may remain connected or use a different contact, allowing the audible call alert to come through. So a loose headset jack can produce no voice while still letting you hear the call signal.

That’s why this fault fits the symptom. Tightening or reseating the headset jack should restore both voice and signaling.