RTS DSR Grey Purple Blue Green Figure 2. Signal description and protocol. This pin is attached to the metal chassis and, in turn, to the third conductor in the power receptacle. Furthermore, if the two DTEs draw their power from different and distant power transformers, a ground potential may flow through pin 1 and result in a shock hazard or equipment damage. Data should not be transmitted until the DSR, DTR, RTS, and CTS circuits are all asserted.
Computer indicates to the modem that it wishes to transmit.
RTS is usually reserved for half-duplex circuits and the computer has to check with the modem to make sure the line is not busy with an incoming character code. CTS also requires that DSR be asserted by the computer and that CD be previously established. When the telephone line is used for voice and data communication, the computer must re-test DSR before reestablishing data communication. Indicates that the computer will accept telephone calls from the modem. If DTR is not asserted, the modem will not answer the telephone when it rings.