Appendix 1: Pulse Signal Detection - North Star MDS-A-O User Manual

APPENDIX 1. PULSE SIGNAL DETECTION
Some steps in the checkout procedure will require test equipment
capable of distinguishing a signal containing pulses from a DC
signal. Anyone of the following will suffice.
1. Use of an oscilloscope is best since the shape and frequency
of the pulses can also be determined.
2. Use a logic probe that detects pulses.
3. If the board is being assembled for use with a HORIZON, then
use a counter on the motherboard to divide the frequencies
down to the audio ranqe and then play the result through a hi-
fi amplifier. To do this, remove the 74LS161 at location 70
on the motherboard. Then attach the test probe wire to jumper
20
pin
16 (this is the input to the divider). Next, take the
output of the divider at jumper 1BA pin 11 and connect to the
AUX input of the audio amplifier. Finally, connect the AUX
input ground on the audio amplifier to signal ground on the
motherboard. This arrangement will divide high frequency
signals
by
4896 and thus put the resulting signal in the
audible range. Thus a 4 MHz signal will be heard as a tone
one octave higher than a 2MHz signal.
4. Construct the "probe" shown in figure IC on a piece of
cardboard or perf-board. This probe converts high frequency
signals to DC signals. The voltage of the resulting DC signal
will be proportional to the duty factor of the tested wave
form.
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