The day that began touch-tone dialing

The operator was almost like your personal secretary making that call for you!

Pretty much. It almost had to work like that though. Placing a coast to coast call could take up to an hour, depending upon the route taken.

I've gotta wonder though, if there was ever an instance of operators having some fun by taking a call and actually routing it around the country a few times before terminating it at the appropriate party. I've actually seen a call routed all the way around the world by some techs "pranking" someone.

From a recent Telecom Digest, for those who might be interested...

Date: Wed, 13 Nov 2013 10:39:14 -0800 (PST)
From: HAncock4 <withheld@invalid.telecom-digest.org>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: 75th anniversary of crossbar service  
Message-ID: <e50cbd1d-fb4c-46e9-ba32-488ff0fb855e@googlegroups.com>

In 1938 the first crossbar switch (No. 1) was installed.  Crossbar
advanced the concept of common control of the switch beyond what panel
switches had achieved.

Also in that era Bell Labs developed improvements in step-by-step
allowing for very small "community dial" offices (see below).

Lastly, in 1938 the model 300 'combined' telephone set was introduced,
along with the 1A key system.

Excerpts from the Bell Labs history:

  The basic idea of a crossbar switch-to provide a matrix of n by m
sets of contacts with only n + m actuators to select one of the n x m
sets of contacts-was proposed early in the automation of switching.
In 1913 a patent application was filed by Western Electric for J. N.
Reynolds for a crossbar switch, and the basic patent was issued in May
1915. The device was based on contact elements multipled in one
direction, as in a panel bank.

   Although the panel system had been providing excellent service and
meeting the needs of heavy traffic in large metropolitan offices, a
number of advantages that the marker-type crossbar system could
include were felt to be important to the future of providing service
economy and flexibility in large cities. (This was the start of the
services evolution made possible with common-control switching.)  By
selecting trunks in the marker, it was not necessary to assign trunks
in fixed group patterns. They could be identified nonconsecutively and
spread over several switches or terminal groups.  This feature was
particularly attractive for large trunk groups serving PBXs where
terminations not identified by directory numbers could be reached by
"jump hunting" to other terminal groups . It meant that traffic could
be distributed evenly over the switches. For the first time alternate
routing was possible.

The use of precious metal contacts would reduce or eliminate the
electrical noise in circuits caused by vibration created in the
contact brushes or wipers of panel and step-by-step selectors. By
using common control with crossbar switches in the network, one was no
longer tied to the characteristics of the switch in determining the
form of signaling to be employed; therefore, it was envisioned that
higher-speed signaling between new system offices and shorter call
completion times could be realized. An objective in designing the
network was to minimize the relay equipment required to be associated
with a call throughout its duration and preferably to concentrate
these relays in a so-called junctor relay circuit in a link or trunk
circuit. These capabilities were achieved from the very beginning in
the No. 1 crossbar system.

   The first No. 1 crossbar office was placed in service in Troy
Avenue, Brooklyn in February 1938. It initially served 1400
telephones.  Prior to the cutover, more than 350,000 test calls were
placed through the system starting in September 1937. This
installation was unique since it was the only No. 1 crossbar system to
be installed without a line choice connector between the terminating
markers and the line link switches.

   The second No. 1 crossbar office, and the first large installation,
was placed in service in July 1938, serving 16,000 telephones from the
East 30th Street telephone building in New York City . Here for the
first time the elaborate PBX features were introduced into the system,
for example those that permitted jump hunting and busy testing of
nonconsecutively numbered PBX trunks as part of the same group. All of
these features, plus reduced maintenance costs together with the
advantages enumerated earlier, proved to be quite successful and
demonstrated not only the increased flexibility of crossbar switching
over the panel machine-switching system, but also its economic
viability for use in large metropolitan offices.  Many features were
later added to the No. 1 crossbar system, including automatic message
accounting (AMA), automatic number identification (ANI), auxiliary
senders, and even a new wire spring version of the originating
senders.

  At the peak in April 1970 of No. 1 crossbar service, there were 325
terminating entities serving 7.25 million lines. The last new
terminating marker group was installed in Philadelphia in 1969, and
the last originating marker group in Chicago in 1970.

Crossbar tandem:
   With crossbar switching it was possible to provide a crossbar
switch link between the incoming trunks and senders (registers) so
that different senders could be selected from different groups,
depending upon the class of service of the incoming trunk. This meant
that the trunks could serve panel, crossbar, and step-by-step offices
each with their own type of pulsing (revertive, multifrequency, and
dial pulse).  The remainder of the crossbar tandem system was almost a
copy of the originating switchtrain of the No. 1 crossbar system,
except that the incoming trunks took the place of the district
junctors, and of course there were no line link frames (see
Fig. 4-12). For this reason it was considered a part of the No. 1
crossbar development and not given a separate code identity. The first
crossbar tandem systems were placed in service in late 1941, in
Detroit, Manhattan, and San Francisco.

  In some metropolitan areas, particularly New York City, individual
message registers per line were provided for charging purposes.
Generally the register was scored once for each call. As the dialing
distances increased, complex district selector and junctor circuits
were developed for the panel and No. 1 crossbar systems that permitted
the multiple scoring of registers on the answering of the call, as
well as additional scorings at the beginning of each overtime period.
[also known as message units, bulk billing or measured service].

Community dial offices (step by step):

   In small offices, operator functions were located remote from the
switching office. The maintenance needs were so infrequent that
resident craftspeople were not necessary.

   The success of and demand for small offices after the depression
stimulated a new equipment design with uniform-size frames and switch
types that were packaged for easy engineering and installation.  This
system, developed by Bell Laboratories, was known as the "355A".
Among the features was a new combined line and cutoff relay as well as
a separate optional "line lockout" relay for use of lines with a high
incidence of line faults.  The first installation was cut over in
Batavia, Ohio in 1939. A total of about 3500 offices serving about 4
million lines demonstrate the success of this development. There is
more of this code of switching system manufactured and placed in
service in the Bell System than any other code at any time.

  Many individual innovations continued to be made in the stepby- step
system. For example, an arrangement was added to provide for early
detection and operator interception of permanent signals in 1963, and
also the timed disconnect of connectors when only the called party
goes on-hook so that he or she may originate a new call.  Other
improvements to maintain the step-by-step system as a viable member of
the Bell System network are described elsewhere in this chapter. The
step-by-step system provided automatic service for more Bell System
lines than any other switching system when it reached its peak of
24,440,000 lines in 1973.

Ever heard a dial tone? By the human ear it is 90 HZ. Curious. When first implemented it was done using twisted wire pairs. Frequency response was optimized as 3kHz Flat and then C-message weighting (response curves optimized for certain frequencies). The bottom end of the response curves were usually kneed below 300Hz or so.

Just how did, does a subscriber hear that 90 Hz so loudly?

[Answer] The human ear responds to the lowest product of combinations of frequencies. It is essentially a biological equivalent of a diode mixer. It ‘hears’ the lowest intermodulation product of two frequencies: 250 Hz and 340 Hz.....amazing, huh?

...when it reached its peak of 24,440,000 lines in 1973.

I remember that. I was in HS at that time, and we were one of the first areas, iirc, to be upgraded to an ESS.

Gone went the 5-digit local dialing and we had to use all seven digits after that.

The new switch also offered new features that you could pay for, too, such as 3-way calling/conferencing/call waiting.

” In some metropolitan areas, particularly New York City, individual
message registers per line were provided for charging purposes.
Generally the register was scored once for each call. As the dialing
distances increased, complex district selector and junctor circuits
were developed for the panel and No. 1 crossbar systems that permitted
the multiple scoring of registers on the answering of the call, as
well as additional scorings at the beginning of each overtime period.
[also known as message units, bulk billing or measured service].”

This brings back memories of customers disputing message units and the pen register tests.It was a pain in the butt.

“That IS interesting isn’t it...”-

Actor James Woods’s character’s reply to Angela Bassett’s character when she said to him, “What IS interesting is that it recorded exactly 18 hours of it.” from the 1997 movie “Contact”.

“Did you know that area codes were originally laid out by population density?
This was to minimize the pulse dialing overhead that would tie up the long distance lines without providing revenue.”

Close. Actually based on incoming call density.

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