[GreenKeys] DTE etc

[Jim Haynes]

On Sat, 24 May 2008, eugene at hertzmail.com wrote:

> I am likely wrong, but I recall DTE/DCE as Data Terminal Equipment (the
> thing a person uses) and Data Communications Equipment (like a modem).
>
> A DTE connected to a DCE requires a straight through cable (pin 1 to pin
> 1, etc)
>
> Two DTEs connected together require a NULL Modem cable which puts Tx of
> one device onto the Rx of the other and vice versa.
>
Right.  Now another factor is that the RS-232 spec applies strictly to
a connector mounted on the modem (data set) and the cable end coming
from the DTE ("business machine").  When there is a connector on the
DTE itself, as on the back panel of a computer, that isn't covered by
the standard.  PCs are all the same, but for DTE in general you'll
find all kinds of variations in the gender of the connector and in the
pin assignments.  Back when I was involved with CRT terminals we had
to make quite a variety of different cables to connect the terminal to
a modem or to a computer.