The zero reference level used to apply and measure voltages in a system.
Note: A potential difference may exist between this reference level and the ground potential of the Earth, which varies with locality, soil conditions, and meteorological phenomena.

A method of signaling from a terminal or subscriber loop to a switch, in which method one side of a cable pair is temporarily grounded.

In radio transmission, a surface wave that propagates close to the surface of the Earth.
Note 1: The Earth has one refractive index and the atmosphere has another, thus constituting an interface that supports surface wave transmission. These refractive indices are subject to spatial and temporal changes.
Note 2: Ground waves do not include ionospheric and tropospheric waves.

The interface or transition point between the isolated and integrated ground planes. The ground window can be a dimensional area around a bus bar or the bus bar itself. After passing through the ground window, there shall be no additional paths to ground, intentional or unintentional, inside the isolated ground plane. [T1.313-1997]

1. A circuit using a common return path that is at ground potential.
Note: Earth may serve as a portion of the ground-return circuit.
2. A circuit in which there is a common return path, whether or not connected to earth.

A type of analog voicegrade access line signaling that requires the customer interface (CI) to provide a ground on the ring conductor at the network interface (NI) to initiate service requests. [T1.401-1998]

1. In frequency-division multiplexing, a specific number of associated voice channels, either within a supergroup or as an independent entity.
Note 1: In wideband systems, a group usually consists of 12 voice channels and occupies the frequency band from 60 kHz to 108 kHz.
Note 2: this is ITU-T group B (formerly CCITT group B).
Note 3: ITU-T Basic Group… (Read More →)

See facsimile.

In a communications network, a predefined address used to address only a specified set of users. Synonym collective address.

A service feature that (a) enables a controlling telephone to place a call to a specified number of telephones simultaneously, (b) enables the call to be recorded, (c) if any of the called lines is busy, enables the equipment to camp on until the busy line is free, and (d) rings the free line and plays the recorded message.