Communication Ports


In computer networking, a serial port enables external modems to connect to a PC or network router via a serial cable. The term "serial" signifies that data sent in one direction always travels over a single wire within the cable.

The prevailing standard for traditional serial port communications historically has been RS-232. These serial ports and cables are the same used for PC keyboards and other computer peripheral devices (see sidebar). Serial ports and cables for RS-232 PCs generally feature 9-pin DE-9 connectors, although 25-pin DB-25 and other variations exist on specialized hardware. The alternative RS-422 standard applies on many Macintosh computers.

Both of these standards are gradually becoming obsolete in favor of USB or FireWire standard ports and serial communication.

Also Known As: COM port

Pin Layout

Commport diagram

Comm Port DB9 Pin Layout

For a standard DB 9 port connectors are as follows:[1]

  1. Data Carrier Detect
  2. Received Data
  3. Transmitted Data
  4. Data Terminal Ready
  5. Signal Ground
  6. Data Set Ready
  7. Request to Send
  8. Clear to Send
  9. Ring Indicator



  1. AGG Software. 2011.

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