Line signaling is a class of
telecommunications
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
signaling
In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...
protocols. Line signaling is responsible for
off-hook,
ringing signal
A ringtone, ring tone or ring is the sound made by a telephone to indicate an incoming call. Originally referring to and made by the electromechanical striking of bells, the term now refers to any sound on any device alerting of a new incoming ...
, answer,
ground start {{refimprove, date=January 2008
In telephony, ground start is a method of signaling from a terminal of a subscriber local loop to a telephone exchange, where one side of a cable pair is temporarily grounded to request dial tone. Most middle 20th-ce ...
,
on-hook unidirectional supervision messaging in each direction from
calling party to
called party and vice versa. After an off-hook, line signaling initiates
register signaling to accomplish the exchange of
telephone number
A telephone number is a sequence of digits assigned to a landline telephone subscriber station connected to a telephone line or to a wireless electronic telephony device, such as a radio telephone or a mobile telephone, or to other devices f ...
s of called party and in more modern line-signaling protocols, the calling party as well. While register signaling occurs, line signaling remains quiescent unless the calling party goes on-hook or an abnormal cessation of the call occurs, such as due to equipment malfunction or shutdown or due to
network
Network, networking and networked may refer to:
Science and technology
* Network theory, the study of graphs as a representation of relations between discrete objects
* Network science, an academic field that studies complex networks
Mathematics
...
outage upstream in that call-attempt's series of spanned trunks.
Line signaling can be conveyed in a single
DS0
Digital Signal 0 (DS0) is a basic digital signaling rate of 64 kilobits per second (kbit/s), corresponding to the capacity of one analog voice-frequency-equivalent communication channel. The DS0 rate, and its equivalents E0 in the E-carrier system ...
channel of a
trunk
Trunk may refer to:
Biology
* Trunk (anatomy), synonym for torso
* Trunk (botany), a tree's central superstructure
* Trunk of corpus callosum, in neuroanatomy
* Elephant trunk, the proboscis of an elephant
Computing
* Trunk (software), in rev ...
. In modern
PCM
Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the amp ...
telecommunications, line signaling is represented by the ABCD bits in DS0 #16 of an
E1 or a selected DS0 within a
T1.
Line signaling can also be conveyed within the channels being supervised, as in the original T1 scheme which used one out of every eight bits for supervision, or with
robbed bits of a
superframe
In telecommunications, superframe (SF) is a T1 framing standard. In the 1970s it replaced the original T1/D1 framing scheme of the 1960s in which the framing bit simply alternated between 0 and 1.
Superframe is sometimes called D4 Framing to a ...
format, or as
in-band signaling
In telecommunications, in-band signaling is the sending of control information within the same band or channel used for data such as voice or video. This is in contrast to out-of-band signaling which is sent over a different channel, or even ov ...
, e.g. as in L1 signaling where 2280 Hz tone pulses are used.
References
{{DEFAULTSORT:Line Signaling
Telephony signals