A choke exchange is a
telephone exchange
A telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital syst ...
designed to handle many simultaneous call attempts to telephone numbers of that exchange. Choke exchanges are typically used to service telephone numbers of
talk radio
Talk radio is a radio format containing discussion about topical issues and consisting entirely or almost entirely of original spoken word content rather than outside music. Most shows are regularly hosted by a single individual, and often featur ...
caller and contest lines of radio stations
and event ticket vendors.
Motivation
A central office might only have physical plant resources to handle ca. 8% of allocated telephone numbers, based on historical call traffic averages. A choke exchange has trunk facilities to other exchanges designed in a manner that high call volume is handled through the ''choke'' connection rather than overwhelming the rest of the local telephone network. Other local exchanges have a limited number of direct trunks (junctions) to the choke exchange, which may only serve one or more customers, such as a radio station contest line, which may experience many simultaneous calls. But instead of calls being overflowed to main or tandem routes shared with other calls, the unsuccessful callers receive a
reorder tone
The reorder tone, also known as the fast busy tone, or the congestion tone, or all trunks busy (ATB) tone is an audible call progress tone in the public switched telephone network (PSTN) that is
returned to a calling party to indicate that the cal ...
from their local or tandem exchange. If the calls were overflowed to the tandem route, the caller would receive a
busy tone
Reanno Devon Gordon (born 24 January 1979), better known by his stage name Busy Signal, is a Jamaican dancehall reggae artist.
Biography
Reanno Devon Gordon p/k/a Busy Signal was born in Saint Ann Parish,Johnson, Carolyn (2006)A Very Busy Chil ...
from the exchange serving the radio station, and the sudden peak would disrupt calls between other customers.
With
common-channel signaling
In telecommunication, common-channel signaling (CCS), or common-channel interoffice signaling (CCIS), is the transmission of control information ''(signaling)'' via a separate channel than that used for the messages, The signaling channel usually c ...
(CCS), e.g.,
Signalling System No. 7
Signalling System No. 7 (SS7) is a set of telephony signaling protocols developed in 1975, which is used to set up and tear down telephone calls in most parts of the world-wide public switched telephone network (PSTN). The protocol also perform ...
, separate choke exchanges may not be required for these customers.
Examples
Examples of choke exchanges in North America have included:
One of the early choke lines (exchanges) was instituted due to a widely advertised contest by a local radio station in the Miami/Fort Lauderdale area.
WHYI-FM
WHYI-FM (100.7 MHz) is a heritage contemporary hit radio station. The station is licensed to Fort Lauderdale, Florida, and owned by iHeartMedia. Y100 broadcasts at an effective radiated power of 100,000 watts from its 1,007 foot transmitter, whic ...
advertised their "Last Contest". The top prize was an automobile. Since the advertising lasted over a month, there were a very large volume of calls when they announced for people to call in. There were so many calls that the local exchanges ran out of dial tones. This caused major issues since at the time if a caller had no dial tone, the caller could not dial at all. After it was over, the area emergency services filed complaints, and were heard. Shortly afterward the 305-550 exchange came into being. The first number on it was 305-550-9100 (for Y100 radio station). Due to the issues involved because of the "Last Contest", this may have been what caused the creation of the choke exchanges.
See also
*
Routing in the PSTN
References
{{reflist
Telephone exchange equipment
Telephone numbers
Telephone numbers in Canada
Telephone numbers in the United States