Wireless cameras have taken the spy gadget market by storm, and there are now far more wireless options than wired. There are two different frequencies commonly used in cameras: 1.2G and 2.4G (1.2 GHz and 2.4 GHz). It should be noted that only 2.4G cameras may be sold in the USA on ebay, but by explaining the difference you will better understand the benefits and limitations of 2.4G vs 1.2G

1.2G used to be the standard frequency on the market due to its low cost and longer range. Because 1.2G is half the wavelength of 2.4G it theoretically goes twice as far for the same amount of energy. While 2.4G has less range, the manufacturers have found ways of making the signal much more accurate. 1.2G cameras have something called "frequency drift," which means that over time, as the battery gets weaker, the frequency of the signal changes. That means you can't leave a camera and transmitter alone for a few hours and come back and still see a good picture. You would have to be there the whole time watching it. 2.4G transmitters in cameras can usually transmit at a frequency split into 4 or 8 channels (one per camera), which means that you can run up to 8 cameras at once and there will be no drift or overlap between them. 8 camera setups can be extremely expensive however, so for most people the 4 channels systems are the way to go. You can only run one or two 1.2G cameras at once (and you can only get the two working at once if they are factory preset) 1.2G also passes through walls and glass a lot better than 2.4G, and seems better able to round corners.

When buying a 2.4G camera, look to see if there is a frequency selector on it. That will come in handy in case it's interfering with another wireless device you have setup, or if you decide to add more cameras later.

No big deal if there is not a frequency selector though! Many great cameras are preset to a specific frequency. The standard channels are: CH1 2.414, CH2 2.432, CH3 2.450, CH4 2.469.