What Is an A/B Switch?

Front of A/B Switch, RadioShack Model 15-1217. Image property of Matthew Torres, tv.about.com

An A/B switch is a very useful television accessory that allows two RF/coaxial devices to connect into a single RF/coaxial input.

It's a switcher that has RF inputs rather than RCA. You can toggle between two separate coaxial signals on a single viewing display. They connect to 75 Ohm cable and their design varies in style from a simple, metallic casing to a plastic design with remote control capabilities.

Here are three common scenarios with examples of how the A/B switch could be utilized:

Scenario 1

Own an HDTV, subscribe to analog cable and use an antenna.

  • Solution Since most HDTVs have a single RF input, you’d need an A/B switch to connect the analog cable and antenna to the RF input on the HDTV. The result would be the ability to toggle between the two RF signals without disconnecting cables.

Scenario 2

Own an analog DTV, use a DTV converter, antenna, and VCR. You want to continue to watch TV on one channel while the VCR records another.

  • Solution: Since the DTV converter controls the incoming signal to the VCR, you’d actually need two accessories to make this happen - an A/B switch and splitter. Connect the antenna to the splitter, which split’s a single input into two outputs. The two cables would go on separate paths until reunited at the A/B switch. ​Read more about this scenario.

Scenario 3

Want to monitor two camera feeds on a single viewing display.

The cameras output is RF, so a coaxial cable is needed. The viewing display only has one coaxial input.

  • Solution: You would connect each camera to the A/B switch then you could toggle between camera one and camera two.