cmV35CTS is a read-only enumeration reporting the current state of the Clear To Send input signal on a V.35 port, part of the standard hardware flow-control handshake. An administrator checks this when data isn't flowing over an otherwise physically connected V.35 circuit, since an off CTS would block transmission at the hardware level. For example, if cmV35CTS stays off(1) while cmV35DSR and cmV35DCD both read on, the operator would suspect a flow-control or cabling wiring issue specific to the CTS lead.