--- jpero_at_sympatico.ca wrote:
> > ...why add a third voltage unless it's something like -5VDC).
>
> Easily done, pick off a 5V to -9V DC to DC converter unit from NIC
> that has BNC connector. Completely self-contained, feed it w/ 5V and
> you get -9V with decent current since that coax RX/TX IC ran hot.
I happen to have a quantity (several dozen) of +5 to -12V converters,
new on the static slab... we had to add them to our Qbus COMBOARDs
because some flavors of Qbus boxes don't provide the -12V we needed
to feed our 1488s and 1489s. Personally I wouldn't have minded if
we'd gone with something like a MAX232, but we were driving two sync
serial ports with full hardware handshaking - we probably would have
had to use two or three MAX232 chips per serial line, plus tantalum
caps (this was back in the days of the first-generation MAX chips).
I think we kept using 1488s and 1489s because our engineers were
concerned about long cables and signal quality and they trusted the
older line drivers. I can't imagine why else we'd pay over $10
each for the voltage converters. Well over. OTOH, back in those
days, MAX232 chips weren't cheap and neither were the caps.
-ethan
__________________________________________________
Do You Yahoo!?
Yahoo! Sports - Coverage of the 2002 Olympic Games
http://sports.yahoo.com
Received on Tue Feb 19 2002 - 19:33:08 GMT