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6ft. DB-9 Female to DB-9 Female Null Modem Cable Beige


Quick Overview

6ft. DB-9 Female to DB-9 Female Null Modem Cable Beige

Availability: Out of stock


DB9 female to DB9 female, 7 conductors, shielded, molded

The purpose of a null-modem cable is to permit two RS-232 DTE devices to communicate with each other without modems or other communication devices (i.e., "DCE"s) between them.

To achieve this, the most obvious connection is that the TD signal of one device must be connected to the RD input of the other device (and vice versa).

Also, however, many DTE devices use other RS-232 pins for out-of-band (i.e.,hardware) flow control. One of the most common schemes is for the DTE (the PC) to assert the RTS signal if it is ready to receive data (yes, it DOES sound backwards, but thats how it works), and for the DCE (the modem) to assert CTS when it is able to accept data. By connecting the RTS pin of one DTE to the CTS pin of the other DTE, we can simulate this handshake.

It is also common convention for many DTE devices to assert the DTR signal when they are powered on, and for many DCE devices to assert the DSR signal when they are powered on, and to assert the CD signal when they are connected. By connecting the DTR signal of one DTE to both the CD and DSR inputs of the other DTE (and vice versa), we are able to trick each DTE into thinking that it is connected to a DCE that is powered up and online. As a general rule, the Ring Indicate (RI) signal is not passed through a null-modem connection.

Additional Information

  • Receive Data 2 3 Transmit Data
  • Transmit Data 3 2 Receive Data
  • Data Terminal Ready 4 6+1 Data Set Ready + Carrier Detect
  • System Ground 5 5 System Ground
  • Data Set Ready + Carrier Detect 6+1 4 Data Terminal Ready
  • Request to Send 7 8 Clear to Send
  • Clear to Send 8 7 Request to Send

Additional Information

SKU CAB-18990
UPC 736983901118
Manufacturer CableMax
Length No
Color Beige
OS Support No

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