OR gate with two 555 - del00014

This shows how to OR gate two 555, when one 555 cycles at a low frequency a valve turns on an off, the second 555 stretches the ON duration of the pulse with a diode OR gate. 

The OR output uses sample and hold to get the stable analog data from a sensor after the actuator has gone OFF, this ensures correct reading. 

555 is a fundamental Mixed Signal Circuit as it can be made into a VCO using Pin-5. If you see old exar databooks, you can see 555 and PLL and Tone decoders all applications compiled in one base. I feel the Venerable Signetics 555 "Architecture" and Intersil ICL8038 'CMOS' were inspiration behind early communication chip designs, Moving from Bakelite Telephones to Compact Push Button Electronic Phones and more.