@Ajeesh: I understand that, and have implemented it too before and even in this project too, 8 address lines and 4 data lines, that has been taken care of. The thing is that I need only one of the 4 units working at a time so that they all dont load the antenna at the same time. I want them working cyclically, which is why I would require powering the 4 units on and off separately. The address and data bus run through both HT12E and HT12D. I need to find a way to send/receive the serial data to/from the encoder/decoder to specific RF modules, not all at a time.