This is a typical 3 ½ digit TTL counter. We found it in the September 1973 issue of Radio Electronics magazine. The circuit is to be powered by 5 V. It can be expanded to more digits.
The circuit shown in the figure is suggested by Allegro Micro (www.allegromicro.com) and consists of...
This circuit is a variation of the common grid dip meter, having been found in a 1975 publication on FETs....
The time obtained in this circuit, from a 1978 publication, depends on R3 and C. R3 can have...