Polarity Guard

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 won’t 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.

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Polarity Guard kit for the TouchTone Ericofon
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