bobmay

My Grandstream GXP2000 supports the MWI. I am sure it is not high voltage
(90v) like analog MWIs use. This phone has a 5 volt power supply. The MWI is a LED. I would think the light is driven via data sent to the phone via IP.

jzawacki

Actually, most VoIP phones that have a MWI will work. We have tested Polycoms, Grandstreams, and Linksys phones and all have MWI's working fine. Voltage does not come into play with VoIP solutions.

But, if your using an ATA, the analog phone plugged in needs to support the broken dial tone for it to work. On my ATA (Grandstream) I have a "Call Prog Tones" page I can set the different tones. In the table for the MW Tone, it has the following configured:

Freq1 (Hz) : 350
Freq2 (Hz) : 440
Cadence On (x10ms) : 10
Cadence Off (x10ms) : 10

So, when there is a message waiting, it plays the dial tone for 100ms on, and then 100ms off. My analog phone can detect this and turn the MWI on.

EDIT: Without manually picking up the phone, so the phone must regularly pick up the line and check the dial tone. :END EDIT

Also, any VoIP phone that supports PoE can handle 48V (Which is the PoE standard), it just drops that down when it gets to the phone.