Re: MMJ Stranded

[G. Morgan <sealteam6@xxxxxxxxxxxxxxxxx>]

chasbo@xxxxxxxxx Wrote:

>Google MMJ, and one of the hits will bring you to Wikipedia for a
>reasonable explanation.


Thanks. I've always used the rs485 box/cord that comes with the PTZ
controller, it never dawned on me someone could try to plug a phone in
it!

http://en.wikipedia.org/wiki/Modified_Modular_Jack

The DECconnect Modified Modular Jack (MMJ) is a variation of the 6P6C
modular connector and was developed by Digital Equipment Corporation.
The main difference from the conventional modular connector is that the
hook is toward the side instead of the center of the plug, making it
impossible to insert a standard modular cable plug such as those used
telephone or Ethernet applications. MMJ connectors are used on Digital
minicomputers, such as the PDP-11, VAX and Alpha based machines and to
connect terminals, printers or serial console servers.

The six conductors of the DECconnect MMJ connector are used for the main
signals in RS-423 serial communication: Tx and Rx for the data
transmission and DSR and DTR for handshaking. The transmit and receive
signals are differential, i.e. each signal is the voltage difference
between two conductors, as opposed to a voltage on a single connector
relative to a common reference. But one can in practice wire these
signals to an RS-232 device, which uses the common reference method, by
combining the lower voltage sides of each signal to the RS-232 signal
ground line. For this type of connection there are a number of models of
conversion adapter.

When connecting two DTE devices such as a computer and a printer, the
Digital BC16E crossover cable is used.
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