Simple circuit for a single 10 ms pulse when closing a contact switch
If I were going to design such a circuit, I would borrow techniques from the traditional transistor multivibrator.



simulate this circuit &ndash; Schematic created using CircuitLab
If you run the simulation, you'll see that it produces one output pulse for every six input pulses. The lockout period is just over 500 ms.
Adjust C1 and R4 to control the output pulse width.
Adjust C2 and R6 to control the lockout period.
R2 and D2 make sure that the output pulse is the full width even if the switch closure is shorter.
D3 and D4 are required because the supply voltage is so high relative to the reverse BE breakdown voltage of the transistors. If the circuit could be run on, say 5V, they could be eliminated.

Note that my original circuit shown above (now slightly modified to save a part) will &quot;auto repeat&quot; at about a 2 Hz rate if the switch is held down. A slight additional modification (C3, R7, R8, below) eliminates this behavior, giving one pulse per switch operation, regardless of how long it is held.



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