Need a cheap "binary" AM transmitting circuit I'm posting this in a forum because i'm not really sure what to search for online. I need a circuit that transmits a one or a zero, basically I have a sensor and i want it to turn something on or off remotely. I was thinking about using an AM oscillator crystal, the range does not have to be far, like 20 feet. Most circuits I looked at were transmitting a frequency, carried on the AM - so i'm not really sure how I would just transmit an on/off state. I guess i could transmit like <1kHz for off and >2kHz for on, but i'm sure there is an extremely easier way to do this. Any Ideas?