Third party Door Phones that typically connect to an available CO/Trunk Port. A visitor presses the call button on the door phone and the phone system will ring a list of programmed phones.
Door Openers: a door pone door opener module can be added to allow the control of opening a door lock for entry into a building or facility.
Most newer model phone system have the capability to page thru all of the phones. If an external pager is need for a large facility or a ware house a third party paging or public address system can be added.
Music or a message can be played about a business or it's offering while callers are on hold.
For the phone repairman phone tools are need to perform installations, repairs, and diagnostics.
In locations where electrical storms are more likely we have devices that will protect the incoming line and electrical circuits from lightning strikes and surges.
All that is need is an analog station port and a conference phone can be added in a conference room for clear souding conference calls.