Hardware Flow Control (RTS/CTS)

Used only by devices that explicitly require it---hardware flow control is disabled by default on most devices. For devices that require hardware flow control, the PortMaster activates the Request To Send (RTS) signal on pin 4 of the RS-232 connector when it can receive data from the attached device. Similarly, output from the PortMaster occurs only if the attached device activates the Clear To Send (CTS) signal on the modem line on pin 5 of the RS-232 connector.