The TBUS is a rear-board connector on each module in the iT Series. The transmitter modules place 24 VDC power onto the TBUS along with digital and analog signals. The transmitter only transmits digital data; it does not receive any digital data from the TBUS. In turn, the alarm module only receives data from the TBUS. They do not transmit data to the transmitter through the TBUS. The alarm module also receive its power through the TBUS connection.