Telos Zephyr Xstream - Manual (Page 371)

USER’S MANUAL
Appendix 10 – Glossary 359
Robbed Bit Signaling A signaling scheme that “borrows” bits on each T1 channel for use as
signaling channels. On SF T1’s there are two bits, the A bit and the B bit in each direction. On ESF
T1’s there is also a C and D bit in each direction, although they are rarely used. Using these bits,
various older analog trunk interfaces can be emulated over a T1. For instance, dial pulse address
signaling using 10 pulse per second (rotary style) digit groups over these bits. Since robbed bit
signaling interferes with the least significant bit, only 7 bits can be used for sensitive data
applications, leaving only a 56kbps channel for data applications. See also CAS and CCIS.
Rollover See Hunt Group
S interface The electrical interface between the NT1 and the Terminal Adapter or other ISDN
equipment. ISDN equipment with built‐ in NT1’s do not necessarily provide access to the S
interface (the Zephyr Xstream, Zephyr, ZephyrExpress and Telos TWO do). Multiple devices can
share an NT1 by connecting on the S interface. Also known as the S passive bus.
S׎ European term for ISDN BRI. See BRI and ISDN2.
S2M European term for ISDN PRI. See PRI and ISDN 30
Sealing Current Unlike telegraphy, teletypewriter and POTS lines, most digital lines (such as
ISDN) use a voltage rather than current mode of operation. Sealing Current allows a controlled
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.
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”. 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. 3) Also sometimes used
generically for other brands of similar equipment. See also SLC‐ 96.
SPID‐ Service Profile Identifier On the “National ISDN”, “AT&T Custom PMP” and “Custom
DMS” ISDN BRI protocols, the Telco switch must receive correct SPID(s) from the CPE before it
will allow access to ISDN service. Intended to allow multiple configurations on ISDN lines shared
among different types of CPE equipment. While your SPID may include your area code and
telephone number, the SPID is distinct from the telephone number. For the National ISDN,