Gene Heskett wrote:
You can still buy external modems that support the RI line. This line was transmit only on the modem, and receive only on the computer (or other equipment) end. It is used where you do not want the modem to auto-answer, but you still want to have full communications with it. For example, you want to be able to use it for outgoing calls, but only answer incoming calls at specific times or specific conditions. Other then modems, I don't recall the RI line being used.Unforch, the hardware side is only half of the story, the handshaking to assure good data is the other half, and that can get fairly complex too as it appears there is more than 1 interpretation of the '7-wire' protocol now so widely used with the db9 connector cuz even that leaves 1 empty pin. The RI is rarely connected or used, although some modems may have exerted it back in the dim reaches of time 2 decades ago.
Now, when it comes to handshaking, the biggest problem I have run into is when one side is set to use hardware handshaking, and the other end is set to use software handshaking. This can be a BIG problem with some USB to serial converters, because not all of them support the hardware handshaking. I have also run into one or two that do not appear to do any buffering, so they are like using a 16450 UART, and at higher BAUD rates, tend to lose data.
Mikkel -- Do not meddle in the affairs of dragons, for thou art crunchy and taste good with Ketchup!
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