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From: John Higdon <>
Subject: Re: Prefix '520' For Los Angeles Radio Stations
Date: 25 Sep 89 07:04:41 GMT
Organization: Green Hills and Cows

In article <>, 
(Joe Talbot) writes:
> Stations often are forced to pay foreign exchange and milage charges
> just to get service, because that service MUST be on a choke system.

The three stations I work with that have choke prefixes do not pay any
mileage. One simply because the 575 is served out of AXminster, their
local office. The other two had previously been served out of AXminster
but moved about a half-mile over the line into ALpine. An appropriate
tear here and an "offer" for some Pac*Bell editorializing there, and
the charges magically vanished.

I understand that another station in town, served out of 95 Almaden,
has a bunch of 575 lines used for some promotion and they also do not
pay any mileage. I'm not sure why (but there is someone on this system
who *does* know--hint, hint.)

Which reminds me of the stormy beginnings of the choke network in the
SF Bay Area. (Oh no, here comes another story, Martha!) It was about
1966 and one of the rock 'n roll AM stations discovered contests
(really give-aways). Technicians in the 95 Almaden office were noticing
these instantaneous overloads of the trunks and the crossbar switching
equipment. In 1966 it was ALL crossbar. It didn't take long to
determine who was the culprit.

Phone company people were faced with a problem. Obviously they couldn't
design the network to handle that peak demand on an occasional basis,
and yet they couldn't be faced with periodic shutdowns that also
prevented emergency calls from being placed. One of the suggestions was
to tell the radio station that they couldn't "abuse their telephone
service" in that manner any longer upon pain of disconnection. The
radio station couldn't see the problem. "We only have four lines for
the contest. How can we possibly be causing any trouble?"

Of course, they had no idea of the trouble caused when hundreds of
calls were directed at one number. Trunks would become jammed with busy
signals (or reorders when the busy tone trunks would fill up) and
normal calls would be blocked. Looking at the problem, they decided
upon creating a special exchange that would have limited trunking and
not share trunks with any other prefix. That way, the special exchange
could busy out without affecting any other service.

Hence was born the choke network. But this is not the end of the story.
In 1972, some DJ at the big 50,000 watt rocker "discovered" how the
choke network worked. He was furious to find out that callers could
actually be blocked from calling him. He created a major stink which
spread to other radio stations and ended up with representatives from
Pacific Telephone and all the area stations in a conference. The long
and the short of it was that PacTel insisted that it had created the
choke network as a "service" to the stations, explaining that the only
alternative was "contest prohibition". They made their point, the DJ
was put in his place, and as an offering of good will, the area
engineers were treated to a grand tour of 95 Almaden, the downtown
office. (For you locals, the DJ was Tom Campbell, who hosted "KLOK
Talk", where this issue came up.)

Even so, from time to time, some DJ suddenly discovers that when he
dials the request lines from an office extension, it's busy (reorder)
and no request lines are in use. I have a canned explantion that
usually calms him/her down.
        John Higdon         |   P. O. Box 7648   |   +1 408 723 1395      | San Jose, CA 95150 |       M o o !

Date: Sun, 20 Apr 1997 20:30:27 -0700
From: John Higdon <>
Newsgroups: comp.dcom.telecom
Subject: Re: Radio Call-In Contest Regulations (Steve Summit) wrote:

> I've speculated that special contest numbers are
> used which are known to all of the switches in a metropolitan area, so
> that the load of returning busy signals to N-1 callers can be
> distributed among all of the CO's, rather than swamping the one switch
> attached to the contest line (and tying up lots of trunks).

This practice (yes, it did exist -- I even hosted a radio talk show
dedicated to the topic back in the seventies) was known as a "choke
network". A prefix was designated as a "high volume" exchange and all
radio stations using lines for contests and requests were required to
obtain numbers in that special exchange. Stations not served by that
particular central office were required to haul it in via foreign

It worked like this: a very limited number of trunks were used to
carry calls from each central office to this particular prefix. The
number was usually around two. That meant that if there were two
people from a particular office calling any station's request lines,
the third caller and all subsequent callers to try would get "all
trunks busy" (a fast busy signal). What bothered station owners was
the fact that any station in the area holding a contest would
effectively shut down all other stations' request lines for the
duration of the contest.

Telco argued that unless this procedure was used that the entire area
could be shut down by one contest -- and indeed one such event
triggered the implementation of the choke network in this area. Telco
insisted that by implementing the choke network, the stations were the
beneficiaries since the alternative was to forbid the use of the
telephone for contests.

> Also, if there's anything to this, what enforcement powers does the
> telephone company have?  If a radio station conducts an unauthorized
> contest, can the phone company cut off their service?  Fine them?  Get
> them hauled off to jail?

The usual threat, never realized, was to cut off the station's
service.  Holding a contest was not a crime, nor was it a tariff
violation, but it came under the purvue of maintaining service to
customers. The radio stations, as much as they complained about the
concept of the choke network, were a pretty cooperative bunch.

I speak of all this in the past tense because in the era of SS7 and
intelligent routing networks, trunk management can be done on the
fly. A virtual choke network can be created instantly. As a result,
the old choke exchange has fallen into disuse.

However, telco never bothered to inform stations that they no longer
needed those expensive foreign exchange lines, and many stations paid
for these circuits for years after SS7 made them unnecessary.

John Higdon  |    P.O. Box 7648   |   +1 408 264 4115     |       FAX: | San Jose, CA 95150 |   +1 500 FOR-A-MOO    | +1 408 264 4407
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