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94 June 2007
What technology is used in the
customer sensors above the grocery
store doors to detect an approaching
customer? Are these units available
new or surplus anywhere?
#06071 Bert Henscheid
I need to interface a GPS engine
serial data out to two different devices.
I would also like to isolate the three
units from each other. Can the serial
data output from a GPS engine drive
two opto-isolators directly, and if so,
would the output of the GPS be
conected directly to the isolator input?
Next, are there opto-isolators that have
one input and two or more outputs?
#06072 Charlie Willwerth
Saint Augustine, FL
I would like to do some kernel
debugging and the software I am using
requires the use of one PC to monitor
another PC. In the past, this would be
done using a null modem cable
between the two serial ports. Now with
only USB ports, I am wondering how to
create a null modem cable. One
thought would be to get two USB to
serial port adapters and hook a null
modem cable between them. I’m
not sure that would work, and even if
it did, a more direct approach and
explanation would be much appreciated.
#06073 John Huseby
How can I vary the 60 Hz line
voltage frequency by very small
amounts? I have an expensive electric
clock that keeps very bad time. I'm
thinking if I could adjust the frequency
going to the clock, I could correct
this problem. Either a commercial piece
of equipment or a schematic would
I need a simple circuit that would
supply a two second on pulse and be
off for 10 to 12 minutes. It should
repeat this cycle over and over again.
The on pulse would drive a 3 VDC
relay. This would be powered from a
5 VDC power supply. Any ideas?
Is the new Microsoft operating
system Vista back compatible? I have
many programs on Astronomy from
Windows 98 vintage, on floppies, that
cannot be duplicated.
#06076 Lyle A. Nelson
Devils Lake, ND
How hard would it be to make my
APC UPS more usable during extended
power outages by using 12 volt Optima