Error description: After ringtone ends, the speakerphone starts hissing. Picking up the handset will end the hissing. This only happens for ringtone w=3 (Classic ring tone) which ships as default for ringtones Classic 1-4. You can also just play the ringtone from the ringtone selection menu to simulate the same behavior. SPA504G on latest firmware 7.6.2f.
I found a discussion from five years ago: https://community.cisco.com/t5/voice-systems/spa504g-white-noise-form-speaker-after-blf-alerts-on-phone/td-p/3238527 which seems to describe the same exact problem, but no solution or workaround.
Can anybody advise? Thanks for your help.
UPDATED 01-31-2020: I just tested a brand new phone with shipped firmware 7.5.2 (no configuration, just network hook-up and ringtone testing) and found that only ringtones 5 through 9 (waveform w=2) work fine. More testing on other phones shows that waveform 3,4,5,6 have that problem while 1,2,7,8,9 do not. Sadly uploaded custom ringtones show the same problem. Any hint as to how the waveform relates to the problem would be greatly appreciated.
