In a nutshell a telephone entry system is the communication device you install at the gate (or entrance door to the building) where visitors can call the home and request entry. Residential units will consist of a "call button" as it only dials the home number whereas commercial systems will dial many different tenant numbers. Most telephone entry systems (tes, call boxes, intercoms, telephone boxes, dial pad...) have a keypad to enter codes to open the gate or keep it open for longer periods of time. Telephone entry systems are a must, an integral piece of gate automation - you don't want to "run" outside to open the gate for each visitor. For residences you will often need a gooseneck post to mount the system so your visitors can call comfortably from their car window. Generally, you will mount the system 10'-12' away from the gate to allow room for the front of the car while you push the call button from the car window. Residential systems do not require a dedicated telephone line to operate. Commercial systems on the other hand, require a dedicated line so they can utilize that line to dial to the different tenant's numbers.