The wiring for telephones includes two wires, green (positive) and red (negative). Rotary
phones never cared if the green and red were wired correctly (correct polarity). When
TouchTone telephones were invented, the very nature of them demanded that polarity be
correct. If one of these vintage TouchTone phones were plugged into an incorrectly wired
outlet, they were unable to dial out. You can receive calls and the phone will ring, but
you cannot dial out. In the late 1970s they developed a device called a Polarity Guard and
after that all phones incorporated this. What it does is automatically compensate if a
phone is wired backwards. This is why a vintage TouchTone phone wont work on an
outlet and a modern phone will. The outlet is reversed, and the modern phone is
compensating. There are two remedies for your situation. You can either re-wire the phone
outlet or the phone (swap the green and red around), or you can install a polarity guard.
The polarity guards I sell are very easy to install and are very small so they fit into
just about any telephone.
Inside the phone there are two wires you will move. The first is going to terminal 'F' on
the network block. You will remove the white wire from this terminal and attach it to the
terminal on the polarity guard that corresponds to the green wire. You then attach the
green wire from the polarity guard to terminal 'F' on the network. The white wire from the
polarity guard will go to terminal 'C' on the network. From terminal 'C' you will remove
either a blue or a brown wire and attach it to the white terminal on the polarity guard.
If you are just going to just stuff the polarity guard in the phone out of the way, I'd
suggest wrapping it in electrical tape first to prevent any short circuits. You can also
put 2-sided tape on the guard and stick it securely in the phone. The size of the polarity
guard is 1.75 inches by .75 inches.
Shipped within the USA
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Polarity Guard kit for the TouchTone Ericofon
$8 + $3 Shipping