From: utzoo!watmath!watcgl!dmmartindale Newsgroups: net.unix-wizards Title: Re: Padding on Ann Arbor Ambassadors &c Article-I.D.: watcgl.222 Posted: Thu Mar 3 18:22:17 1983 Received: Thu Mar 3 23:47:43 1983 References: sri-unix.5221 I believe that the Request to Send and Clear to Send lines were provided for use with half-duplex modems - RTS told the modem to turn on its carrier and CTS indicated that the modem was stable enough for transmission of data to begin. Full-duplex modems may provide no useful information on these signals. In any case, they certainly aren't propagated to the modem on the other end of the line, and there are many terminals in the world connected to computers by modems. The only possible means of flow control under these circumstances is some form of "in-band" signalling, whether it be XON/XOFF or ENQ/ACK or acknowledgement of received data. Modem control leads are useful for controlling modems, but not for end-to-end things like flow control.