Telos Zephyr Xstream User Manual page 364

USER'S MANUAL
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. See also Hybrid.
Frame A unit of data which is defined by the specific communications protocol used. See Line
Format, T1.
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 or ISDN trunks are used. See also Ground Start Trunk.
GR‐ 303 See SLC‐ 96
Grade of service This is simply the ratio of calls blocked to total calls in a decimal form.
Therefore, 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. See also
Blocking.
Ground Start Trunk A type of telephone trunk where the request to make an outgoing call (i.e.
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. Ground start lines are
sometimes used with equipment designed for Loop Start lines. This may or may not work ‐
generally it serves to prevent outgoing calls while incoming calls work normally. Telcos may call
these "ground start lines". See Loop Start Trunk. See also Glare.
HDB3‐ High Density Bipolar 3 An E1 line coding method. This is the more modern line coding
method of the two commonly available. See Line Coding, T1. See also AMI and B8ZS
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 also LDN.
Hybrid A device which converts from a two‐ wire signal such as POTS lines (or a 2‐ wire
intercom) 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 ‐ 1) InterExchange Carrier "Long Distance" carrier. Handles Interlata and interstate calls.
Also referred to as IXC. 2) International Electrotechnical Committee A European standards
body best known for the power plug now used throughout the world for AC power cords for use
on office equipment and computers.
Appendix 10 – Glossary 352