Telos TWOx12 - Page 204

TELOS TWOX12 USER’S MANUAL
GLOSSARY OF TELEPHONE TERMINOLOGY
APPENDIX 4 192
E-1
- A common type of digital telephone trunk widely deployed outside the US and
Canada. Has 30 available 64Kbps channels (called DS∅’s) plus a signalling/control
channel.
ETS 300
- The pan European ISDN protocol standardized by ETSI. This protocol is
used throughout Europe and has been adopted in many other countries outside the USA
& Canada. See MSN.
Exchange
- Another name for a Central Office. See CO.
Four Wire
– A circuit path using separate pairs for send and receive. This term is also
used when referring to digital channels that inherently have discrete send and receive
paths, regardless of the number of pairs (or other media) used.
Glare
– On a POTS line an incoming call is signaled by periodically applying an AC
ring voltage to the line. Since there is a semi random period before the ring, and pauses
between rings, it is possible to seize a line which is “about to ring” (and answer a call)
when attempting to place an outgoing call. When this scenario happens it is called
glare. Glare is much less likely if Ground Start trunks are used. See Ground Start
Trunk.
Grade of service
- This is simply the ratio of calls blocked to total calls in a decimal
form. So a grade of service of P.08 would represent 8% blocking. Telephone tariffs
regulate the acceptable average grade of service which must be provided on public
networks.
Ground Start Trunk
– A type of telephone trunk where the request to make an
outgoing call (ie request for dial tone) is made by briefly grounding the Tip conductor.
Many PBX system use ground start trunks as they are less prone to glare than Loop
start trunks. See Loop Start Trunk. See also Glare.
Hunt group
- A group of telephone channels configured so that if the first is busy
(engaged) the call goes to the next channel, if that channel is busy it goes to the next
channel, etc. Hunt groups may hunt from the highest to the lowest, the lowest to the
highest, or on some other arbitrary pattern. But the order of hunting will usually be
fixed, beginning with one channel and working through (“hunting”) until an unused
channel is found. The term may have originated back in the old manual switchboard
days when the operator literally hunted for an unused jack to plug a cord into. This
arrangement is very common in business scenarios where a single incoming number
(the Listed Directory Number) is given to the public, but multiple incoming channels
are supported. See LDN.
Hybrid
– A device which converts from a two-wire signal such as POTS lines to a
four-wire system (separate send and receive paths) such as used in the pro-audio world.
While this task is theoretically quite simple, the fact the impedance of most phone lines
varies widely across frequency complicates matters. The Telos 10 telephone system
was the first practical DSP based hybrid and applied the then brand-new technology to
this problem,
IEC
- InterExchange Carrier. “Long Distance” carrier. Handles Interlata and interstate
calls. Also referred to as IXC.
ILEC
– Incumbent Local Exchange Carrier. A local Exchange Carrier which entered
the marketplace after the enactment of the 1996 Telecom act;. i.e. a telephone company
which is neither an Indie nor an RBOC. See LEC and CLEC.