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| No well appointed home should be without one of these. |
This is a classic cord PBX (Private Branch Exchange). When a call came in a light came on under the jack corresponding to the calling line. The operator took an idle cord and plugged it into that jack. A switch mounted on the keyshelf allowed her to connect her headset to the cord and speak with the caller. She could then plug the other end of the cord into the jack for the desired line. Another switch allowed her to ring the called telephone. Lights told her the status of the calls on each set of cords so she would know when to disconnect the cords. A buzzer was provided so that she would know ifthe board needed attention when she was not sitting directly in front of it.
This board has provision for 80 extensions, and 10 outside trunks. The board has space for 15 cord sets (so it could support a maximum of 15 calls at one time), but only had 9 cords when I obtained it. I have since been able to find 1 additional cord set. I suspect the local phone company (a small independent company in Pennsylvania) charged on a per cord set basis.
I used to have a cat, named Radar who loved it when I operated the board. He would come running whenever he heard the buzzer. He would search and search trying to figure out where the buzzing was coming from. Then he would try to catch the cords as
they fell back into position after a call was taken down.
When I was a small child I used to annoy the lady at the local Sears while she
ran one of these.
Again this is a classic cord PBX, but one which the Bell System put a lot of effort
into making more maintainable. The cord and trunk circuits
are each in individual modules, which plug into the back frame of the board. To get this board
into my house I had to disassemble it.
The board is so well modularized, that the entire disassembly and reassembly took less than 1
hour!
Other modern features were the use of push buttons instead of keys for ringing, and cords mounted near the face of the board, so as to give the operator an open desk space for writing etc.
A much publicized feature was the ability to 'split' a cord circuit
so that an outside call could be announced to the called party without the calling party
hearing 'Oh not him again!'.
This was the last Cord switchboard designed by Western Electric.
Instead of wood, the cabinet is made of Fiberglass, and the shelf and face are metal.
Instead of a lever switches, the operator's talk key is a button which lights up when depressed.
Ringing is done automatically when a cord is plugged into an extension jack, obviating the need for ringing keys on each cord set.
A clock was also provided at the lower right side of the board.
The board pictured here was used as an attendent's position for a dial PBX.
Incoming calls came in on jacks near the bottom of the face (indicated by the orange lamps), and were completed
directly to the station jacks at the top of the face.
Since extension users dialed their own originating calls, the station jacks have no lamps associated with them.
Attendent calls (dial 0) from extensions also came in on a row of jacks near the bottom of the face.
Made for small businesses, this board is really just a repackaging of Bell's 505 series from the
1930's.
Instead of cords, lever switches are used to connect stations and trunks. The board can handle 12
extensions and 5 outside lines, and supports a maximum of 5 simultaneous conversations at once.
I first saw one of these in a Civil Defense trailer. The intent was to provide service over
tie lines between the Police, Fire, and other civil agencies in the event of a disaster
in my home town. Later I saw one at the local Chevrolet dealership.
I built this machine from actual central office parts. It is an example of the technology used to
provide dial service in small to medium sized cities and towns. It was first employed in the early
part of the 20th century and continued in use into the early 1990s. It is referred to as 'step-by-step'
because the switches follow the pulses produced by the customer's rotary dial, and hence set
the call up 1 step at a time. Of course a real central office would have had rows and rows of this
equipment. Even though I have only heard it a couple of times, the
sound of step-by-step office at peak traffic time is something I will never forget.
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| Details of Switch Mechanism The central shaft can move up 1 to 10 positions, and also rotate 1 to 10 positions, thus allowing the switch to choose 1 out of 100 possible contacts. |
My switch is a 3 digit system, however through he use of a feature known as 'digit
absorption', it gives the impression of being a 4 digit switch. In the 1950's, this
feature allowed many older offices to be upgraded to the then new 7 digit standard
numbering plan without massive changes.
The Dial Tone, Busy Tone, and Ringing signals are supplied from a motor-generator set (shown at left) made for moderate size PBX (Private Branch Excahnge) service. There are actually two motor-generators - the second takes over in case the first one fails.
Four sealed twelve volt batteries supply steady power, and keep it running in case of a power outage (they also can light a few emergency lights in my house).
By the way, this machine serves us quite well as an intercom within our house!
This model was one of the first mass produced sets with the transmitter and receiver
mounted in a common handset. The bell and induction coil were mounted in a separate
wall mounted 'Bell Box'.
Subscribers could request that these be painted. Mine is a very nice white, but I must
admit I was attracted to it for a much sillier reason:
The number on it starts with 
The standard phone when I was growing up. 1937 was its first year. Until 1942 when World War
II made metal scarce, the case was metal.
This is one phone you didn't have to hold while dialing! Later models used plastic,
and came in colors. The bell and induction coils were mounted in the base, obviating the need for
the
'Bell Box'.
The '300' set was also made in colors. White was fairly common. Colors such as Rose, Pink,
Green, Blue and others were made, but are rare finds today. One problem was that early
color plastics
were not very stable, and tended to shrink with time. The result is that it is very difficult to open these
sets up without damaging them, and if you leave them open for any appreciable time they
are liable to "unstretch" to the point that the case cannot be replaced.
This phone was a 300 set arranged for multiple line use in businesses. It came in 4 and 6 button
varieties. The leftmost button was almost always a hold button.
The buttons could be illuminated to show which lines were busy, on hold or ringing.
Sets intended for use without illumination had solid black buttons
instead of clear plastic. I use this particular phone everyday, and it still seems to be in great shape.
This was the 'new' model when I was a child. 1949 was its first year. One feature
of this model was its ability to operate satisfactorily over long rural lines.
Later versions of this model used a varistor
to compensate for line length, but this one uses a small lamp to do this.
This model was available is several colors,
including red, white, light blue, yellow and grey, and of course black.
Two customer visible features which distinguished this phone from the earlier 302 set
was the flat backed handset, and an adjustment for ringer volume.
Back in the pre-divestiture (actually 'pre-carterphone') days owning your own phones
and connecting them
to the Bell (or even an independent) network was a heinous crime. Many businesses, wanting to minimize their
telephone
expenses installed systems like these to keep the intra business load off of their
Bell switchboards (thereby keeping them smaller and less costly).
The small town bank for which my grandfather worked had a system like this.
Each phone was wired to every other set,
and lever switches were used to choose the party you wished
to call. In modern terms this would be called a peer-to-peer network.
There was no central 'switch'.