AT&T Long Lines

Switched Network Management

Radio-Frequency Interference Investigation

The Eastern Region of AT&T Long Lines used this specially-equipped motor home to search for "quiet" sites for satellite earth stations and to locate sources of interference to terrestrial microwave transmission.


The following lists of courses are from:
Long Lines Operations Catalogue of Training Courses
Headquarters Operations Training
Cincinnati, Ohio
March 1973

Course materials are not available from this site, but individual course descriptions can be posted upon request. Contributions of course texts and audio-visual materials, in physical or electronic form, will be much appreciated.

Lenkurt Technical Training School, 1950

Traffic Operations

Plant Operational Error prevention

In a complex activity like the operation of a nationwide broadband telecommunications system, there are numerous opportunities for human error. In the Bell System, such mistakes were called Plant Operational Errors, or POEs. Examples of POEs would be shutting down a piece of equipment while it was carrying traffic, or connecting a plug to the wrong jack causing communications to be misrouted.

Because a single coaxial conductor or microwave radio channel could carry thousands of simultaneous telephone calls, or a television network's programming for the entire country, Long Lines personnel took great care to avoid service disruptions on these broadband facilities. Motivational displays like those shown below served as day-to-day reminders of the need to be vigilant in preventing POEs.

Many Long Lines stations had the capability of establishing temporary connections among the station's broadband communications channels, and among various devices within the station. These connections, called "patches", were used to bypass equipment and channels which failed or were being taken out of service for routine maintenance, and to reconfigure the network to meet unusual, short-term service needs. For example, a spare radio channel could be patched to carry a special television broadcast from the town where it originates to a nearby city, where it would be patched into one of the national network "loops".

Patches were established by plugging "patch cords" - lengths of flexible cable with plugs at both ends - into jacks located on "patch bays". A "patch bay" was a vertical panel holding a number of jacks, each jack being permanently wired to an individual broadband communications channel or piece of equipment. A given function might require more than one patch connection. For example, since a broadband channel carries communications in only one direction, patches on two channels would be required in order to establish a two-way link for voice traffic.

To indicate the purpose of a particular patch and help prevent the accidental removal of active connections, an AT&T committee developed paper patch cord identification tags which would be attached to the patch cords being used. The tags were furnished in various colors to distinguish among multiple patches which might be in place simultaneously for different purposes, allowing technicians to easily locate all of the patch cords being used for a given task.

Disaster Recovery


Other Motivational items

Western Electric

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Updated on May 13, 2010 at 20:25 by Albert LaFrance