hay ... @alumni.uark.edu (Jim Haynes) wrote
Sounds when there is an incoming call that needs attention. It also lights a signal lamp on the board. This circuit is always called a "night alarm".
The typical manual switchboard "audible alarm" was a buzzer. Bell System PBX buzzers tended to make a rapid clicking sound rather than a buzzer, that sound was a bit more pleasant.
In service, busy switchboards kept the buzzer off and operators watched for signal lights, both on the jackface as well as supervisory signals from cordpairs. In light service, where operators would be doing other tasks, the buzzer was kept on.
The "night alarm", if present, was a separate loud bell, intended to someone from a distance or wake someone up.
Cord PBXs had "night connections". When the switchboard was shut down for the down, connections would be made with outside trunks and designated extensions to receive calls. Modern (1960) cordless dial PBXs had a more sophisticated system: after hours a separate bell (old style wall mounted bell boxes) would sound. Anyone who wanted to answer would dial a special code and would get connected to the incoming outside call.
In the Moutain Bell history, "Muttering Machines to Laser Beams", they describe in detail life with a home switchboard. The telephone company inspected the home very carefully, down to how clothing was arranged to bureau drawers. My impression was that service WAS available 24/7, late at night the alarm would wake the operator up. In the small communities there would normally be very little night traffic, but people would need to call the doctor or report a fire. During WW II, a long distance call from a hometown serviceman might come in.
In my own town, the local switchboard serving a few hundred lines, had two positions with a full time operator and a part time assistant. (The assistant was in high school at the time and still lives in town, and kindly shared her experiences with me*.) Anyway, the switchboard was in a private home; my point being even a busy two position board could be in a house.
During ESS trials, the lab men considered "taking over" the switch late at night which meant taking the exchange out of service. A few minutes before the shutdown an emergency call for a doctor came through. They realized how critical telephone service is, even at 3am in a small town.
*In 1954 the town went dial. The young woman was transferred to a nearby city to work a dial toll & assistance board. The city board was a totally different experience than the small town board, the city board was very structured while the small town was informal (like "Sarah" in Mayberry). The operator did keep track of where the doctor and policeman were in case of emergency. The small town board did NOT handle long distance, all toll calls were forwarded to the next town where a toll operator handled it.