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DTE (Data Terminal Equipment) - DCE (Data Communications Equipment)

When connecting two RS232 devices one is called DTE and the other DCE. This is legacy terminology from the terminal (teletype then later the PC) connecting to a communications device (modem) where the terminal is the DTE device and the communications device is the DCE device. The reason for the naming is to clarify who is transmitting and receiving on what pins for use with a standard straight through cable.

Standard straight through cables have a one-to-one pin connection. That is to say, if you took the cable out and plugged the DCE device directly into the DTE device it would be same as if a straight through cable where inserted into this connection.

The terminology is important to understand since not all DTE equipment are PC's and not all DCE devices are modems and you cannot use a straight through cable when connecting a DTE device to a DTE device or a DCE device to a DCE device. If you need to do the later you will need a null modem. A null modem is basicly a cable that flips pins 2 and 3 (Tx and Rx) so that like equipment can speak to each other.

RS232 - DTE (Data Terminal Equipment) - 9 pin male pinout (PC Side)

Pin 1 - Carrier Detect (CD) input to DTE
Pin 2 - Receive Data (RD) input to DTE
Pin 3 - Transmitted Data (TD) output from DTE
Pin 4 - Data Terminal Ready (DTR) output from DTE
Pin 5 - Signal Ground
Pin 6 - Data Set Ready (DSR) input to DTE
Pin 7 - Request To Send (RTS) output from DTE
Pin 8 - Clear To Send (CTS) input to DTE
Pin 9 -

reference/rs232_pinouts.txt · Last modified: 2011/05/20 15:54 by jacob