The 4528 is a dual-retriggerable monostable that needs only the timing network formed by R and C to perform this function as shown here. This circuit is triggered on with the positive edge of the input signal. The minimum value recommended for C is 100 pF and Fl can assume values between 10 k ohm and 10 M ohm. Time constant is about R x C. This circuit is not recommended for large time delays; use the 555 CMOS or another. The numbers of pins used in this circuit correspond to one of the two monostable multivibrators of the 4028 package.