I just spent an hour troubleshooting this issue so I thought I would post the solution.
Hardware:
Linksys SPA-2102
Various cordless and corded phones
New addition: Siemens Gigaset A495 DECT 6.0 (with 1 base and 4 handsets)
Symptoms:
- At incoming call, Gigaset A495 will not ring, but all other phones ring
- Gigaset A495 will show caller ID, but will not ring on incoming call
- Can get dial tone from all Gigaset A495 handsets, and all other phones
- Can complete outgoing calls from all Gigaset A495 handsets, and all other phones
Solution:
- Login to SPA-2102 as admin
- Go to Advanced interface
- Click Voice
- Click Regional
- Scroll down to "Ring Waveform"
- Change from the default "Trapezoid" to "Sinusoid"
Verify:
- Gigaset A495 now rings on incoming call
- all other phones continue to ring properly on incoming call
Summary:
It appears that some phones will only ring when presented with a Sinusoid waveform, but not a Trapezoid waveform. If you are experiencing similar symptoms, try the solution outlined above.