DTIM with digial phone service

I install these types of alarms.
First, What is usuallly plugged into the cables main box? Usually it is a jack. This would run to the main phone lines in the house, and allow you to have service at alll the jacks in the house. If this was not the case, then you usually just plug your phone in directly. Either way, the tel #1/2 on the main box is the same principal as the two main lines comming in off the street with the phone company. If there is a jack, get another and a peice of 2/4 strand wire. (If you have a 8 pin bell jack let me know if not follow.) connect the red and green at the main jack to the red and green of the new jack. Plug in the DTIM and go. If it is just a plug in the phone directly then i suggest getting three jacks. plug a regular phone cable from tel 1/2 into the first jack. Then connect the red and green to the next red and green. this is the DTIM jack. Then do the same to connect a phone jack for your phone. I have installed lots of simon 3 systems but never with a DTIM> I also install alot of GE Allegro panels and they come with the DTIMs. Are you having it learn in properly? It should be group 39 on the system. At least it is on the other panels.
Good luck.