Does that mean you have to use the extension cord?

I paid about $20 including shipping for a single channel A/C model. Allegedly the A/C receiver is more reliable then the battery version. If I understand right what happens is when the batteries start weakening in the battery version it isn't that reliable. The A/C version saves you changing batteries all the time. Plus I think the A/C model might be a dollar cheaper -) They look a lot like the model sold by Speedotron. At least the pictures of the Speedotron.