Pulse Width Modulation using the 556 Dual Timer.
Output period is set through the first timer which is a 555 Timer configured as a conventional astable multivibrator.
Output pulse width is set through the second timer which is a 555 Timer configured as a monostable multivibrator. Adjustment is through Rpwadj.
For the saved values:
Period is roughly 1 ms.
Pulse width is adjustable from less than 75 µs to greater than 975 µs.