On Jun 21, 12:33 pm, datajerk <dataj...@gmail.com> wrote:
On Jun 21, 9:47 am, datajerk <dataj...@gmail.com> wrote:
I worked with a lot of RS-232 devices in the mid '80s to the early
'90s. Dumb terminals, modems, printers, Alpha Micros, the Apple II,
short-hall modems, data collection devices, many different RS-232
multiplexers to add terminals to various UNIX systems, etc...
Excluding a few oddballs (e.g. Macs) they all used female DB25
connectors except, IIRC, IBM PCs (and later the multiplexers started
to use RJ45s). The PCs used a female DB25 for the parallel port and a
male DB25 for the serial port. I always thought this was a poor
decision since repairing broken pins on a cable was cheaper than a
device.
As I dug through my vintage serial devices I found a 1985 HP-IL to
RS232C device used to provide a serial port to HP-IL devices such as
the HP41 calculator. It also has a male serial port. That has left
me with the thought that something greater was redefining the
convention or was it simply the PC that started the trend to use male
RS-232 ports primarily on computers?
In any case, what got me thinking about this was the installation of a
newly acquired SSC card for my IIe. Given my history I was neither
shocked or surprised, but it got me thinking.
I plan to build my own cable for the SSC with a male DB25 to conform
with convention and to distinguish it from the female DB25 port I plan
to install for my printer card. Perhaps that was IBM's thinking as
well.
I failed to mention that the SSC came with a female DB25.
From Wikipedia on RS-232, FWIW:
"RS-232 devices may be classified as Data Terminal Equipment (DTE) or
Data Communication Equipment (DCE); this defines at each device which
wires will be sending and receiving each signal. The standard
recommended but did not make mandatory the D-subminiature 25 pin
connector. In general and according to the standard, terminals and
computers have male connectors with DTE pin functions, and modems have
female connectors with DCE pin functions. Other devices may have any
combination of connector gender and pin definitions. Many terminals
were manufactured with female terminals but were sold with a cable
with male connectors at each end; the terminal with its cable
satisfied the recommendations in the standard."