I can only assume that it's a simple oscillator with a feedback resistor
and a cap from the input to ground. Just using a diode on the input,
anode to input, and you can stall the oscillator by pulling the cathode
to ground (low) by a preceeding gate. I use such a circuit in a few cmos
projects now. Or, an npn collector to the input. Saturating the npn will
also stall the oscillator.
Rick

Jinx wrote:

> The 74C14 are single-input gates, so you can't use gate logic
> to turn the oscillator on/off (I presume, as you've not described
> the oscillator circuit). You could send the AC from the oscillator
> through a resistor to another 74C14 gate and ground the input
> of that 2nd gate with an NPN transistor (and so also ground the
> AC via the resistor). That would give you "1" (sound off) "0" (sound
> on) control at the transistor's base
>
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