I have a D735 on 3CX hosted service.

After placing an incoming caller on hold, the phone plays a dial tone sound through the receiver earpiece. If the receiver is placed on hook, the sound continues to play through hands free speaker and cannot be turned off.

Dial tone sound plays continuously the entire time a call is on hold but is not audible to the incoming caller.

Navigating to other screens (settings, for example) mutes the sound temporarily but it resumes when returning to the main screen.

The issue is present on both 10.1.175.16 and 10.1.184.14 firmware versions.

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Justin A.

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Joined: 09.01.2025

1 Comment

  1. Justin A.

    Jan 09, 2025

    After spending quite a bit of time this morning trying to track down the cause, here it is: The cw_dialtone option, turned on by default, plays a dial tone sound when a call is placed on hold. Documented here:

    Turning this setting “on” will play a dial tone when a call is being held, signalling the user that he is able to dial a second number. No dial tone is played when this setting is set to “off”.

    Somewhat un-intuitively, the setting apparently behaves differently between the D735 and D862 that I’m testing. I have verified that manually setting the cw_dialtone option to off works.

    Posting this update in case someone else has a similar issue. It is not unique to the D735.