This circuit, suggested by an Electronics World of 1969, keeps a blinking LED for a while when a power outage occurs. Time depends on capacitor C1.
This Hughes circuit is from 1968. Equivalent modern components can be used. The input impedance is...
An interesting application in case of needing to supply an operational amplifier or a very low...
This VCO with the CMS 4046 was found in the August 1994 Electronics Now magazine. The frequency is...