In article <firstname.lastname@example.org>, Robert Bonomi
> In article <email@example.com>,
> <firstname.lastname@example.org> wrote:
>> Back in the 1970s, a standard fixture in almost every business (and
>> even in some wealthy homes) was a key telephone. This has six buttons
>> along the time so that the phone could handle more than one outside
>> line, intercom lines, and HOLD function. I was wondering what basic
>> key systems cost in the 1970-1975 time frame.
> Commonly known as a "1A2" system.
There was an earlier version known as 1A1, and apparently a 1A, 2A, and 2B
The 1A1 units that I have seen, were built as a complete unit, where
the 1A2 systems were modular, using plug in cards for the various
features. I have no information on 1A, 2A, or 2B systems.
>> From what I saw, the pricing was a la carte--every little feature was
>> a charge. One large organization did not bother with line lamps to
>> save money. The "wink-hold" feature, where the line lamp blinked
>> slowly when the line was on-hold, was optional. I never saw a system
>> without a HOLD button, but apparently even that was optional. (I
>> believe later systems, such as ComKey had package prices).
> The button itself, and the mechanical actions related there were universal.
> whether the back-end equipment recognized 'hold' and kept the circuit busy
> was the 'optional' part. Took some additional cards in the card cage.
The phones could be wired up without a KSU, and would operate as a
regular phone, without lights, or hold. The ringers in the phones were
wired to a dedicated pair, and could be strapped to any line, or to
multiple lines via a diode matrix.
The basic KSU had a power supply for the lamps, and a line card for
each line, which handled the hold function, lamp control, and ring
indication. The basis line card was a type 400. Lamp voltage was
The wink-on-hold feature required an interruptor, which plugged in to
the KSU, and provided the pulsed lamp voltage for lines on hold. This
was normally powereed by the 10vac lamp supply, although other
voltages were available.
I worked at a radio station where all the lamps, and interuptors were
powered by 24vdc from a bank of batteries, which also supplied all the
control circuitry within the studios. The PBX (Western Electric 711B
step-by-step dial PBX) was powered by another bank of batteries at -48vdc.
>> Anyway, would anyone know what typical pricing was in the 1970-1975
>> time frame, for the following:
>> - "Hunting" feature so busy calls would go to the next line.
> Handled entirely in the C.O. nothing in the 1A2 had anything to do with it.
> (the CPE was irrelevant, unless you had 'trunk' circuits into a true PBX.)
>> - Two lines, two keysets, line lamps that would blink on ring, but not
KSU without interruptor.
>> - Wink-hold feature.
KSU with interruptor.
>> - Basic manual intercom (push-button to sound buzzer). Sometimes there
>> was a SIG button on the phone, sometimes there was a tiny panel with
>> pushbuttons mounted next to the phone.
KSU with a type 401 manual intercom card in place of a line card.
Signaling was handled by using either a spare button on the phone, or
add-on button(s) wired to extra pairs, and a add-on buzzer powered
from the lamp voltage supply. The buttons in the phone could be
changed from latching to momentary by removing a screw.
>> - Dial intercom, one common channel, one digit automatically sounded
>> desired buzzer.
There were several types of dial intercoms, depending on the number of
stations desired. The smaller ones could be cards in the KSU, or a
>> - Other features of the six button keyset?
You could wire the phones to do many different things. We used to use
the buttons on the phones to provide contact closures to other
(non-phone) devices, and the same for the lamps.
>> - If a residence had a key system was the cost cheaper than a business?
>> Around the 1960s the Bell System came out with a fancier system known
>> as the "Call Director". Did this have any advanced features or did it
>> just offer more line buttons? I know the basic Call Director shell
>> was used as a PBX operator's console, but that was a different phone
>> and included an additional lamp for supervision.
> One of the big features of the call director was idiot lights that
> showed the on/off hook status of multiple extensions. A limited number
> on the phone itself (10? 15?) plus expansion sections with additional
> 25(?) lines/indicators.
> I don't know what equipment was behind it -- had to be considerably
> more than just a 1A2 chassis, probably Centrex -- but all the call
> directors I ever saw had the capability to do a two/three button
> 'transfer' of an incoming call, to a specified extension.
This would have been a Call Director in a PBX type environment, with a
busy lamp field.
The basic Call Director was simply a 1A2 type phone, with additional
buttons/lamps. The earlier ones simply added additional 6 button
strips, and the later ones were 10 button strips. Earlier call
directors were commonly 18 or 30 buttons, and later 10, 20, and 30
buttons. There were also some custom monster phones.
There were some wiring differences between the 6 button strips, and
the 10 button strips.
Normally each line used 3 pairs of wire, 2 for the phone line, 2 for
the button (A1/A), 2 for the lamp (L/LG).
For a 6 button phone/5 line phone, this would be 15 pairs, plus one
for the ringer, leaving 9 spare pairs for add-on devices such as
buzzers, speakerphones, etc, using a 25 pair cable. Some phones were
equipped with 15 or 18 pair cables instead.
For 10 lines, this would require 30 pairs, not including any pairs for
ringer, or add-on buzzers, etc, but by bussing all the A1 leads
together, the spare A1 leads for lines 2-5 could be reused as A leads
for lines 6-9. The same trick was used with the LG leads, thus
reducing the number of pairs needed to 19 (plus one for the ringer),
leaving 5 spare pairs for add-ons in a 25 pair cable. Additional 25
pair groups were added for additonal 10 button rows.
>> Six button keysets are rare to see today, having been replaced by more
>> modern systems. Even the Bell System, before divesture, had developed
>> several new lines, such as ComKey and phones with more buttons
>> (identified by a larger square button with the light within it. Both
>> wall and desk sets had a long row of buttons along the top of the
>> phone. These were out early enough that they were made in rotary dial
>> as well as touch tone.
The phones with more buttons sound like late version Call Directors.
I found a collectors website, with a listing of many many types of
Western Electric phones, including many that most people have never
seen or heard of.
-- Welcome My Son, Welcome To The Machine --
Bob Vaughan | techie @ tantivy.net |
| P.O. Box 19792, Stanford, Ca 94309 |
-- I am Me, I am only Me, And no one else is Me, What could be simpler? --