If you only have one cable in the device box then the switch outlet is likely wired as a switch leg drop. You should see two black wires each connecting to a different screw on the right side of the switch.
4 Way Switch Wiring Methods Electrician101
Light switch wiring common. For those of us using led fluorescent or some other energy efficient bulbs under 20w a neutral is required. A little about the light switch the common single pole switch is one of the simplest electrical devices that you have in your home. The common is usually a wire used on a 3 way switch in this situation it would be either the hot wire or the switch leg meaning the wire that runs to the fixture. These are called terminal screws. At the light the white wire connects to the neutral terminal and the black wire connects to the hot. Observe the layout of the wires.
The 1 pole light switch will have two terminals on it and possibly a third terminal that is a ground connection. Yes there are a few read very very very few switches that dont require a neutral but those will limit you to incandescent only. You should also see a green. In an ideal situation these wires will be wrapped in the same insulation. The most common light switch is the single pole light switch. All they do is interrupt the flow of electricity to a device like a light fixture ceiling fan or a switched receptacle by making closing or turning on or breaking opening or shutting off a circuit.
The neutral wire from the source is spliced to the white cable wire and continues on to the light. The most common requirement of any hardwired automated light switch is a neutral wire. The other wires for a three way are called the travelers and are the wires that connect the switches together. The source hot wire is connected to a switch terminal and the other terminal is connected to the black cable wire.