When using this set-up with HyperTerminal, you should not select a Windows modem driver in the "Connect To" dialog. Instead, connect directly to the relevant COM port. Next, verify that the modems are working by sending information commands such as "ATI1" or "ATI3". If you don’t get a response using these commands, try resetting the modem(s) using the "AT&Z" command. Assuming you do get a response, set one in originate mode using the "ATD" command and the other in answer mode with the "ATA" command. If all is well, you should now be able to type in one terminal window and see the results echoed in the second PC’s terminal window. To return to control mode, type "+++". The advantage of using modems instead of a serial cable between COM ports is that the two PCs can be kilometres apart instead of a few metres. For example, you could connect the house PC to the workshop PC on the other side of the farm.
Author: Filippo Quartararo
Copyright: Silicon Chip Electronics