Intercoms are electronic communications systems that consist of fixed microphone/speaker units that connect to a central control device. There are two basic types of products: hard wired and wireless.
Hard-wired intercoms are connected by cables and are installed in buildings, apartments, offices, and manufacturing facilities. Wireless intercoms rely upon radio frequency (RF) transmission and are used in television stations, broadcast control vehicles, power plants, and communications facilities.
Specifications for hard-wired intercoms include:
- physical dimensions
- power requirements
- system capacity
- minimum cable rating
- maximum length per run
- termination standard
- termination plug type
- installation method
Intercom dimensions are measured in inches (in) or centimeters (cm) and include length (L), width (W), and diameter (D). Power requirements are measured in volts (V) and amps (A). System capacity is the number of units that can be connected to the main console. The minimum cable rating states the number of paired conductors and indicates whether the cable is a twisted pair (TP) or untwisted pair (UTP).
T568A and T568B are common termination standards for intercoms. RJ11 and RJ45 are examples of termination plug types. The installation method indicates whether the intercom installs in a single bay or double bay, and whether the main unit can be installed in a standard three-gang box. Underwriters Laboratories (UL) provides approvals for hard-wired intercoms.
Features for wireless intercoms include:
- physical dimensions
- battery life
Intercom dimensions are measured in inches (in) or centimeters (cm) and include length (L), width (W), and diameter (D). Range is measured in feet (ft) or meters (m). Frequency range is the range of radio frequencies (RF) over which intercoms can operate. Many wireless devices are powered by batteries that are rechargeable or replaceable. Battery life varies with power requirements and length of use. In the United States, the Federal Communications Commission (FCC) mandates compliance with appropriate regulations for wireless communications.