[time-nuts] RS-232 port

Hal Murray hmurray at megapathdsl.net
Sun Aug 9 23:11:05 EDT 2015

> I have an HP Z3805A with the nice faceplate and 6 leds on the front.  I also
> have a Z3801A also with 6 LEDs.  What is the difference in the com ports?
> The Z3805A works fine with a standard 25pin to 9 pin adapter.  The Z3801
> does not.  ...

The  Z3801A comes setup for RS-422.  The board is setup to support both 
RS-232 or RS-422 depending on jumpers or 0 ohm resistors.  Pictures here:

It's pretty obvious after you take one apart and poke around with an ohm 
meter.  You can put a few of them back in different slots rather than the 
actual jumpers in the pictures.

These are my opinions.  I hate spam.

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