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Non-Mitel Chatter / Re: Help finding information on ANCIENT phone system
« on: July 06, 2019, 01:04:21 PM »
I just found this forum and this question. Just HAD to add my limited information to it.
In the late 1970's I worked for GTE Automatic Electric - a small office in Detroit working as an interconnect in 'Bell' Territory. I think this was GTE's experiment to see if they wanted to get into this business. I supported a limited number of the Leich 40 and 80 switches. These had been installed a few years before, but the company had already moved on to the newer GTD 120 PBX (600 pounds and half the size of a refrigerator) and 17A key systems for new installations. We finally got electronic key systems in 1982.
So my memories of this system are 40+ years old and not very clear. (BTW, I am still active in telecom, selling VoIP and digital systems.)
The Leich 40 was about 5 1/2 feet tall, and 3 to 4 feet wide. Inside was a series of vertical 'station', 'trunk' or 'register' bars. The bars were removable (with difficulty) and had rows of reed relays on them. Each reed relay had 4 to 20 contacts. The 80 was wider and had space for more of these bars. I think the 40 had a maximum of 32 extensions and the 80 was 64 or 72. 8 per bar.
When you went off hook a station bar would do a sequence of relay connections to give you dial tone and connect you to a receiver bar. That receiver bar would count the pulses from your rotary-dial phone (No DTMF) and another sequence of relays would connect you either to a trunk bar and a phone line, or to a different station bar. That station bar's relay sequence would select the destination, apply ringing and make the connection when they went off hook. Each of these relay sequences lasted 1-2 seconds and involved very specific chains of relays and contacts depending on the required task.
Troubleshooting involved slowly and methodically tracing the sequence of connections across the relays with live test calls until you found the one that was sticking or not passing along a signal. Then I would use a clean $1 bill as a burnisher to wipe the carbon out of the relay contacts. Then test again and go on to the next sticking relay. A service call to one of these was usually at least half of a day.
In the late 1970's I worked for GTE Automatic Electric - a small office in Detroit working as an interconnect in 'Bell' Territory. I think this was GTE's experiment to see if they wanted to get into this business. I supported a limited number of the Leich 40 and 80 switches. These had been installed a few years before, but the company had already moved on to the newer GTD 120 PBX (600 pounds and half the size of a refrigerator) and 17A key systems for new installations. We finally got electronic key systems in 1982.
So my memories of this system are 40+ years old and not very clear. (BTW, I am still active in telecom, selling VoIP and digital systems.)
The Leich 40 was about 5 1/2 feet tall, and 3 to 4 feet wide. Inside was a series of vertical 'station', 'trunk' or 'register' bars. The bars were removable (with difficulty) and had rows of reed relays on them. Each reed relay had 4 to 20 contacts. The 80 was wider and had space for more of these bars. I think the 40 had a maximum of 32 extensions and the 80 was 64 or 72. 8 per bar.
When you went off hook a station bar would do a sequence of relay connections to give you dial tone and connect you to a receiver bar. That receiver bar would count the pulses from your rotary-dial phone (No DTMF) and another sequence of relays would connect you either to a trunk bar and a phone line, or to a different station bar. That station bar's relay sequence would select the destination, apply ringing and make the connection when they went off hook. Each of these relay sequences lasted 1-2 seconds and involved very specific chains of relays and contacts depending on the required task.
Troubleshooting involved slowly and methodically tracing the sequence of connections across the relays with live test calls until you found the one that was sticking or not passing along a signal. Then I would use a clean $1 bill as a burnisher to wipe the carbon out of the relay contacts. Then test again and go on to the next sticking relay. A service call to one of these was usually at least half of a day.