[Al Skierkiewicz]

C,
The schematic shows that the transmit is simply turned on and off by the processor in the transmitter. Effectively this is just a digital CW signal and the data scheme is coded in the transmit/receive processors. It you varied the temperature or voltage input at the transmit side you might be able to see some correlation to what is actually transmitted. It could be something as simple as a BCD encoding of the transmit carrier. Since the thermometer is used over a relatively narrow range and the resolution is likely 100 degrees or less, the encoded data is not critical. It may even be only necessary to count the on/off transitions of the carrier to determine the data sent. It is also possible to only send absolute temperature when the unit is first turned on and then only send delta temperature since the last transmission. i.e. the first data sent is a long encoded signal of the absolute temperature. The remainder are short bursts indicating the difference in temperature since the last data was sent. This would save battery life as well.