Hx1-Hx2 Manual-1.4.1 - Telos

A14 | appendix 1
amount of current to be passed through a telecom circuit for purposes of “healing” resistive
faults caused by corrosion. Bellcore specifies sealing current on the ISDN U interface in the
USA. The Siemens EWSD switch does not provide sealing current. Most other ISDN capable
switches used in North America do.
SF- Superframe. A type of Line format supported on T1 circuits. The Telco determines the line
format and line encoding of your line. ESF is the preferred Line Format on T1 circuits. See
Line Format.
Silence Suppression- See Statistical Multiplexing.
SIP – Session Initiation Protocol, the most common IP protocol at the time of this writing for
providing telephone service over IP facilities. It is used by most Voice Over Internet Protocol
(VOIP) service providers.
SLC-96 – A Subscriber Loop Carrier Circuit system manufactured by AT&T (now Lucent).
SLC-96 has its own version of T1 framing between it and the CO. SLC-96 and similar “SLIC”
systems may or may not perform a concentration function. The interface is the Bellcore TR-008
or the newer GR-303 interfaces that are specialized versions of T1 intended to allow transparent
transport of analog CLASS features such as Caller ID, Call Waiting, etc. The GR-303
interface is specifically intended to be used as a common point of interconnection between
alternative equipment, technologies, and/or networks (i.e. voice-over-DSL, voice-over-IP,
etc)) and the public switched network. See the following link for additional information from
Telcordia: http://www.telcordia.com/resources/genericreq/gr303/index.html.
SLIC-1) Subscriber Line Interface Circuit, see “Line Card”.
SLIC-2) The equipment used with the AT&T (Lucent) SLCC Subscriber Loop Carrier
Circuit, a system used to multiplex a number of subscriber loops onto a single circuit (usually a
T1 circuit) to reduce fixed costs.
SLIC-3) Also sometimes used generically for other brands of similar equipment. See also
SLC-96.
Smart Jack – see NIU.
SS7 - Signaling System 7. The internationally adopted Common Channel Interoffice Signaling
(CCIS) system. Previous to SS7 the Bell System used SS6 which did not support the International
Standards. SS7 does. It allows for substantially flexibility and power in dynamically
routings calls. An SS7 database lookup is how a call to a mobile telephone user can be handled
transparently despite the fact that the user’s location may change. Also used to determine what
carrier should handle a given toll free call. See also CCIS.
Station Line – A telephone circuit from a PBX to a telephone on that PBX. Since this is a
telephone-to-switch connection it is considered to be a “line”. See Line and Trunk.
Station Side - The user side of a PBX. The side of the switch that the telephones are attached.
Also, occasionally called the ‘line side’. The main reason for distinguishing between this and the
trunk side is that certain customer related features (Such as Hold and Transfer) are inapplicable
to most trunks. See also Trunk Side.
Statistical Multiplexing- A method of improving effective bandwidth of a Telco channel.
Statistical Multiplexing takes advantage that there are typically many pauses in a conversation.
By taking advantage of this fact, and not sending the pauses, improvements in efficiency can be
made. Also referred to as silence suppression. See Circuit Switched.
Subscriber- The customer of a Telecommunications company. This term dates back to when
a local Telephone Company was formed at the specific request of a group of customers who
agreed in advance to “subscribe” to the service.