I hope you may know about a product to solve this requirement.
I have a customer with Cisco Call Manager including a VG248. They need a tricky system for their front door intercom for access after hours. Currently they just have an intercom to one internal office. They need something they can use with the phone system that the person can just press a speed dial to contact a specific room? The person at the other end would then just dial a number to open the door.
Having speed dials configured is not a problem; the existing analog phone at the door can be used to dial any of these.
My question is about opening the door remotely by using the phone system (very common feature in small key systems). I was thinking about a small device that emulates an analog phone set on one end and has a relay on the other; when it receives a ring tone it closes the relay for some seconds (activating the mechanism to open the door). Sounds simple but, do you know if this product exists? I was checking the Black Box catalog and found nothing.
Here is one such product that I have heard good things about (but have not used);
Valcom Single Door Answering Device-Activate Door Locks
(Model # V-2901A)
From this link;
Hope this helps!