RS232 itself is a well-defined spec. But you're right. An lot of equipment existed that was only vaguely RS232 compatible. Some of it even predates RS232. F

RS232 itself is a well-defined spec. But you're right. An lot of equipment existed that was only vaguely RS232 compatible. Some of it even predates RS232. For example, the old electromechanical teletype machines send and receive something close enough to RS232 line signalling that you can connect them to a modern computer's RS232 port, if you wire up a tiny analog circuit to convert from telegraph-style current impulses to RS232-style voltage levels. Just set the UART to 50 bps with 5 bit data and 2 stop bits. And don't send anything too soon after a carriage return! Not all UARTs can handle those settings, but that's why such options were in terminal programs back in the day.