AT&T System 85 manual Multi-Appearance Voice Terminals

GENERAL INFORMATION

Multi-Appearance Voice Terminals

A multi-appearance voice terminal gives its user much more flexibility in handling calls than a single-line voice terminal. A multi-appearance voice terminal, represented by a unique primary extension number, has multiple call appearances (buttons with lights) where incoming calls to the number can be answered and outgoing calls can be originated. Incoming calls can ring simul- taneously at all appearances except for those translated as originate-only. As long as at least one appearance is idle, callers will not receive busy tone. When all call appearances, except call appearances translated as originate-only, are busy, callers will hear busy tone unless the incom- ing call is a priority call or the Restrict Last Appearance feature is deactivated. The terminal user must decide the order to answer multiple incoming calls.

The two sub-types of multi-appearance voice terminals are digital and hybrid. Digital terminals generate and receive voice and control signals in digital form. Connection between terminals and the system switch is over 2-pair digital links; no conversion is necessary at the digital line port. Hybrid terminals, as the name implies, combine analog and digital. They are connected to the system switch by three pairs of links; on MET-like hybrid sets, one pair is for analog voice, and the other two pairs are for digital control signals, and on ATL-like hybrid sets, one pair is for digi- tal control signals, and the other two pairs are for analog voice. DC power for all multi- appearance terminals (except for the 7404D and 7407D01B, which are AC powered) is con- ducted from the switch over the digital pairs.

Digital multi-appearance voice terminals have several important advantages over hybrids:

Digital voice terminals can support and control data terminals.

The Digital Communications Protocol (DCP) or ISDN-BRI interface between a digital voice terminal and the system switch supports simultaneous voice and data calls over the terminal’s standard mounting cord.

Digital terminals have a wider selection of adjuncts.

Call information displays are available with some digital voice terminals.

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