32
5-7. Digital Frequency Selection
Frequencies can be switched electronically by using the set-up shown in FIG. 9.
The preset voltages can be digitally selected and applied to the VCF IN BNC.
Although provision for two frequencies are shown, additional frequencies can be
added using redundant circuits. This is convenient in frequency shift keying(FSK)
systems.
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FIG 9. DIGITALLY PROGRAMMED FREQUENCY SELECTION
5-8. Additional Applications
The triangle or ramp output of this instrument can be used at its lowest frequencies
to simulate a slowly varying DC source. This can be used to check threshold levels
of TTL and CMOS logic as well as voltage compactors can be exercised from zero
to full scale to observe defective deflection such as sticky meter movements.
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