The carter system allows the switching of both the hot and neutral conductors because the hot and neutral switch back and forth a 3 way dimmer can not be used the carter circuit was banned in 1923 but i have found them in homes wired all the way up into the 50s and using romex wiring. When the lamp is getting a neutral from both sides it is off.
Carter 61 5 Floor Lamp
Carter 3 way switch. But no communication between top and bottom switch boxes. Hotness voltage enters into the system at one three way type switch which we will call the hot end according to the position of its handle hotness travels on to the next switch on one of the two traveler wires. In such a system against the code for quite a while of course the 2 portions of the socket are either hot or neutral and they switch between the 2 depending on the position of the switches. Instead the top box and the bottom box each sent one conductor to the load. This might seem intimidating but it does not have to be. The trick is to wire the 3 ways backwards with hot and neutral feeding the poles normally used as travellers and connecting the light betwen the two commons.
There will be a hot and a neutral at each of the 3 way switches connected to the terminals normally used for the travelers then the common of each switch connected one to the hot base of the lamp and the other to the neutral shell. That way the cable running to the garage has hot neutral and switched. Not one cable one conductor. The carter system was a method of wiring 3 way switches in the era of early knob and tube wiring. This now obsolete wiring method has been prohibited by the usa national electrical code since 1923 2 even in new knob and tube installations which are still permitted under certain circumstances. This configuration is no longer allowed as the neutral is not present in each switch box.
Conventional 3 way wiring is not very complex. The alternate 3 way switch wiring configuration california or west coast was used as a way to wire 3 way switches and be able to supply line voltage to either switch. 3 way switch wiring diagram. Take a closer look at a 3 way switch wiring diagram. Pick the diagram that is most like the scenario you are in and see if you can wire your switch. If this next switch is the only other switch it is also of the 3 way type and can be called the leg end.
This is often called the california 3 way or similar. A staircase with a light 3 way switches top and bottom. There is a whole chapter about this 3 way set up in the book old electrican wiring by david shapiro. It takes advantage of the light being off when both terminals are hot. With these diagrams below it will take the guess work out of wiring.
Gallery of Carter 3 Way Switch
