Due to a manufacturing problem, one-way audio may be experienced when using a CP-7920 wireless telephone. A short circuit may occur in the speaker wiring on the CP-7920, which results in no audio being heard through the telephone ear piece.
The contact of a speaker spring with the Printed Circuit Board (PCB) may cause a scratch on the PCB. This may result in a short circuit between the speaker spring and the PCB. Manufacturing tests found the failure rate of affected units to be .93 percent.
The problem is likely a symptom of Cisco bug ID CSCed93344 - 7920 Speaker failure results in one way audio.
There has been a change in the manufacturing process to rotate the speaker spring 90 degrees so the contact area is away from the PCB. Due to the low failure rate, only telephones exhibiting this failure in the field should be replaced.