In the mid 1960s Western Union introduced a private line voice service
> called "Hot Line". In essence, a person lifting the receiver of one
> telephone would cause a specified distant telephone to ring over a
> private line. The connection was faster and cheaper than placing a
> conventional long distance call over the Bell System. WU charged by 6
> second increments and at a lower rate; the Bell System at that time
> had a 3 minute minimum. WU says their arrangement was cheaper when
> more than 3 calls a day were made.
> The connection between the two telephones was actually not a dedicated
> private line, but shared use of the WU network via concentrators. If
> a circuit was busy there were alternates.
The article said the service was popular among brokers between field
> offices and the central office serving the stock exchange for calling
> in stock orders. Such calls were normally brief.
> Obviously this service had some limitations since it was telephone-set
> to telephone-set. I don't think this could terminate in a PBX system
> to allow shared use of the line by a whole organization which would
> give more flexibility.
Correct. It was a dedicated line/circuit. Either physical or 'virtual'.
There was minimalist special-purpose 'central-office' equipment for those lines; two ports. When one port went off-hook, it send 'ring' down the other port. Then the 2nd port went off-hook, it was cross-connected to the first one. After both sides hung up, the system reset itself.
I don't know if WU permitted any kind of
> multiple extension sets at the subscriber since a specialized telephone
> set they provided was used.
Pretty vanilla innards -- omitting the dial assembly was common.
A limited (max 3?, 5?) number of extensions _were_ supported/allowed by specific arrangement.
For example, a secretary might want to
> answer the boss's hot/line phone if he was out.
> WU also reported customers wanted to get the service in more cities > than available.
> None the less, it seemed like a pretty good idea for its time.
> Would anyone know how successful this service was and how long it > lasted?
"Ring down" circuits are not uncommon today, although they have been mostly replaced by ISDN -- which gives you call set-up/completion in less time than you can get the handset from cradle to your ear.
At least in Chicago, the telco provided the dedicated circuits -- dry wire pairs (3002, 3008, types) -- and the customer provided the "C.O." gear, as well as the phones.