I installed a new system for a customer that wanted to use some of his older phones with the new system. The problem I'm faced with is that the T7220 phones do not ring on incoming calls. I've put them in the incoming call group with the other phones in the system, but they do not ring. As a matter of fact, they cannot answer the call on any of the T7220's. When there is an incoming call, the phones light up, and when you try to pick up the call, there is a busy signal. Is there another location that I need to activate the extensions in order to have them work like the DT343 phones?
Thank you in advance.

The older digital phones Max 10 and APT supported only on 4 port DHLC.


76xx. and up no problem.

Check load chart in manual 1.3.3

Max load is 44 for both 500 and 1000.
76xx and up load is 1 per phone.
Older digital and APT is 4 per phone.
.

10 7220 and 4 port VM would be 42, leaving room for 2 76xx and up phones.
APT and older digital load is 4 per phone


RTM!!

Saw the chart you referenced, couldn't make heads or tails out of it when I first read it. Your explanation helped. Thank you.
The customer will need to upgrade the 6 older phones they are trying to use. They only bought 5 new phones with the system, in hopes they could use the older ones for the kids rooms and non essential rooms.