Pulse Signal Detection - NorthStar HORIZON Manual

APPENDIX 1. PULSE SIGNAL DETECTION
SOine steps in the check-out procedure will require test equipment
ca~able of distinguishing a signal containing pulses from a DC
si'~nal.
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.
Use a counter on the motherboard to divide the frequencies
down to the audio range and then play the result through a hi-
fi amplifier. To do this, remove the 74LSl61 at location 7D
on the motherboard. Then attach the test probe wire to jumper
2D pin 16 (this is the input to the divider). Next, take the
output of the divider at jumper 10A 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 4096 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.
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North Star HORIZON Computer