Administrator's Guide

Trunks and trunk groups
Issue 5 October 2002 1911555-233-506
■ Wink start — The terminating switch sends a wink start (momentary
off-hook) signal to the originating switch. This indicates that the
terminating switch is ready to receive digits.
■ Delay dial — The terminating switch sends a delay dial signal (an
off-hook signal followed by an on-hook signal) to the originating switch.
This indicates that the terminating switch is ready to receive digits.
Types of address transmission
In addition to seizure and start dial signals, switches have to transmit the digits
and characters for telephone numbers. This is called address transmission. Three
types of signaling are available:
■ Dial Pulse (DP) addressing — A method of signaling that consists of
regular momentary interruptions of a direct or alternating current at the
sending end. The number of interruptions corresponds to the value of a
digit or character (alternating current is not used by switches). The
interruptions usually are produced by a rotary telephone dial, or may be
produced by a sender in a switching system.
■ Dual Tone Multifrequency (DTMF) addressing — Signaling
arrangements (commonly known as touch-tone) that consist of two,
simultaneous, dialing signals. One tone is from a low group of four
frequencies. The other tone is from a high group of four frequencies. Both
tones correspond to digits, letters, or characters (0–9, A–Y, or * and #). One
of the tones (1,633 Hz) from the high group is a spare.
■ Multifrequency (MF) addressing — Signaling arrangements that make
use of only 2 frequencies out of 6 to represent 10 decimal digits (0– 9) and
5 auxiliary signals. MF signals are used for called number addressing,
calling number identification. They also report whether the far end is
ringing or busy.
Analog vs. digital trunks
Analog trunks carry voice and voiceband data communication. “Vo i c e ” means
that sound of any kind is transformed into electrical waveforms and transmitted
within an approximate bandwidth of 300 Hz to 3,400 Hz. “Voiceband data” means
that data is transmitted within the voiceband and requires a conversion resource
(modem) at both ends of the connection. The data-transmission rate for analog
trunks depends on the data-handling capability of the modems in the connection.