The CPU uses tune inputs to tune the frequency synthesizer. The CPU give a signal to the transmitter to send interrogation pulses. The transmit pulses go through a circulator then to the DME antenna.
The transmitter sends a signal to the suppression circuits. During a transmission, the suppression circuit in the DME 1 interrogator sends a suppression pulse to these units:
· DME 2 interrogator
· ATC 1 and 2 transponders (XPNDR)
· TCAS computer.
The suppression pulse stops receiver operation in the other LRUs to prevent damage to internal circuits.