Does any one know a book or web-site that describes the pin-out for a nine pin connector preferably a round nine pin connector.
try this web page, it explains the RS232 protocol and the pins used with a DB9 (9 pins) connector. is easy to understand. microlink .uk/rs232.html
The only round pc connectors I know of are 5-pin and 6-pin. The old style serial connector is 9-pin but it isn't round. Here are diagrams for the round 5 and 6-pin: pinouts.ru/connector/6_pin_MINI-D If you want the non-round serial diagram pin-outs then google for rs232 diagram #
