What is the importance of DCD, DTR, CTS, RTS, and DSR in serial communications

Hello Ktdog,

These are signals that may (or may not) be implemented on an RS-232
connection to help control the flow of data. An old reference, but
still accurate is the LA-100 programmer reference manual at...
  http://vt100.net/docs/la100-rm/chapter1.html


For example, if you have a terminal or computer connected to a modem,
these two devices will use the signals as follows...
  - DCD Data Carrier Detect - a connection is active between the local
and remote modems
  - DTR Data Terminal Ready - the terminal (or computer) is ready to
receive data
  - CTS Clear To Send - the modem will process data from the terminal
  - RTS Request To Send - the terminal wants to send data
  - DSR Data Set Ready - the modem is ready to receive data (i.e., can
be programmed, but may or may not have a connection)

There are a number of good references on this topic. Search using
phrases such as
  DTR RTS explain
to get further information.

  --Maniac