|MODULAR ADAPTER DB25M TO RJ45
Cyberguys item no. 131 2070
|MODULAR ADAPTER DB25F TO RJ45
MilesTek item no. 10-01045
RJ45 8-pin modular to D-sub adapters are widely available for about $2 and are convenient for RS-232 connections. If you have a number of serial devices with different pin-outs, you can make adapters so that any device can easily be connected to another device. These universal adapters are particularly handy for devices such as hubs or controllers that only occasionally need to be connected to a terminal.
All devices are wired the same at the modular jack and the flat modular cable flips the connections. This way, any device may be connected to any other device, regardless of whether it is DTE or DCE.
The RS-232 signals are assigned to pins in the modular plug and jack as follows:
|Pin||Color||Signal name||Remark||Signal source|
|DTE (computer or terminal)||DCE (modem)|
|1||Blue||DTR, HSKo||CD||Data on pin 3 is valid||Jack|
|2||Orange||RTS||CTS||I am ready to receive on pin 6|
|7||Brown||CTS, HSKi||RTS||OK to send on pin 3|
|8||Gray||DSR||DTR||Data on pin 6 is valid|
More details on making RS-232 connections to Macs.
Do not use this pin-out for connecting a modem to the AUX or console port on a Cisco router. Use this pin-out.
Tomi Engdahl compiled a page detailing various "standards" for the pin-out of the modular connector. One such standard is the Yost Serial Device Wiring Standard, which is similar in concept, but not pin-for-pin compatible, to what I have detailed here. The Comtrol Rocketport serial card uses the RJ-45 with another pinout which is described by Jim Price.
Please send your comments and suggestions.
John Neuhaus, WA2JXE
john at jneuhaus.com
Last revised: Tue, Mar 27, 2007