Western Electric
Networks
Sewing Machine -
Automatic Answering Service
"Mirrophone" wire ribbon recorder/player
Telephones -
PicturePhone
- Bell Chime
If you've ever opened up an old telephone
made back in the days when phones were built to last for decades you may have
notice a little metal box with a plastic top. The plastic top has a bunch
of screw terminals with wires coming from the screw terminals to various parts
of the telephone like the dial and bell ringer coil. Well, that metal box
with all those screw terminals is what is known as the telephone's network
circuitry. It contains resistors, varistors, coils and other passive
electronic components that interconnect all of the other parts of the telephone
with your telephone line cord. It actually does a lot more than just
provide a centralized location for hooking up all of those pretty colored wires
in the phone, it provides impedance matching, side-tone, d.c. current blocking
for the bell ringer coil, suppression of voltage spikes, and other functions.
Although all models of these networks were
functionally very similar, some networks were designed to be smaller than their
predecessors in order to fit into the newer telephones like the
Princess and the 2554 wall
phone and the
Trimline
model desk and wall phone. Others had special radio interference
suppression circuitry built into the network to block or greatly reduce
interference from nearby radio or TV stations or ham radio operators.
Schematics for these various networks were
not published for all models by Western Electric - at least not in the Bell
System Practices manuals I've seen. ITT, however, did publish schematics
of the various networks in their copycat telephones made under license from
Western Electric (AT&T). See the
ITT service manual web page
(not on this website) for schematics of these networks plus the
Western Electric Telephones web page for more schematics.
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To help you identify some of these networks I
took some photos with my Sony 5 mega-pixel camera of various networks I have
accumulated which you can view by clicking on the links below:
4228 Network (top and side view)
4228 Network (bottom view)
Schematic
of the 4228
Side-by-side comparison digital
photograph of two types of 425 networks
Individual photos of a
425G network and
425K network.
Some networks were modified for RFI (Radio
Frequency Interference) suppression. Here are schematics of three such
networks:
Here are a couple of photos of a cheap ITT
network. Note the exposed parts and circuit paths. These circuits
will not withstand humid environments or contaminants as well as the Western
Electric counterparts.
