First Electronic Switch - Morris, IL

Bell/AT&T Labs was trying to invent a new type of switching system that didn't have mechanical parts. Their first field trial attempt was the Morris, Illinois experiment from 1958 to 1962. This used a "cold cathode" vacuum tube technology. This experiment lasted a little bit more than  a year and was later scrapped for the fully transistorized 1ESS system in 1965. 


Background on the Morris, IL Experiment

The Morris, IL experiment was conducted between 1958 and 1962. This involved using a stored program control switch that used "cold cathode" gas tubes.

The phones used on the system were rotary, but were 20 pulses per second rather than the regular 10.

The switch was not in use 24 hours per day and customers had two telephones. One was used with the existing #5 crossbar switch, one was for the experimental switch.

The experimental switch didn't have a traditional tone plant, and used an electronic tone plant. These tones were not used in the later ESS system. 

The switch was unable to produce the amount of current required for mechanical ringers. The experimental phones had special electronic ringers instead (the first of its kind)

The experiment ended in 1962 and the project was scrapped in favor of fully transistorized systems, such as the 1ESS (Number 1 Electronic Switching System) which was introduced in 1965.

The following is a plaque that was installed at the central office where the experimental switch was located.

Article from Telecom Digest on the history of Morris, IL (and other ESS research)

Excerpt from the Telecom Digest archives:

From: John Nagle
Subject: Re: Early ESSs?
Date: Mon, 04 Nov 91 02:15:36 GMT

There were a number of experimental electronic switching systems
before the 1ESS. Interestingly, an early Bell System experimental
system, in 1953, involved pole-mounted concentrators remotely
controlled by a #5 crossbar at the central office. Field trials were
conducted in LaGrange, IL, Englewood, NJ, and Freeport, LI. Further
experimental work was done on distributed switching, but the notion of
active components in outside plant was premature; components were not
yet reliable enough. So the 1ESS was, like its electromagnetic
predecessors, designed with all the active components in the central
office.

The system installed in Morris, IL in 1958 was in some ways "more
electronic" than the 1ESS system. Unlike the 1ESS, which uses reed relay
type devices for the actual call switching, the Morris system used
cold-cathode gas tubes. So, unlike 1ESS, Morris had no moving parts.
But Morris required special telephone sets, with active components,
because the gas-discharge tubes couldn't handle the usual 86V ringing signal.
Coin lines, PBX lines, and loop testing, all of which use nonstandard
voltages, were not supported at all. 

While electronic, Morris was only partially solid-state. The
test system had over 2000 vacuum tubes, plus 30,000 gas-discharge tubes.
The test system served only 400 customers, so a big Morris-type system
would have had rather large numbers of vacuum tubes.

Pictures of the Morris switch show a truly strange-looking system.
The gas-discharge tubes had to be illuminated by fluorescent lamps to 
provide enough free electrons so that the tubes would ionize quickly.
So the banks of tubes sat in brightly lit racks with built-in fluorescent
tubes running vertically down the racks.

[Source: A History of Engineering in the Bell System, Switching
Technology, 1925-1975.]

John Nagle

 


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