This circuit uses a 555 (according to the diagram) to generate 50 ms tone bursts at a frequency of 1.5 kHz. The circuit is from an 80's Electronic Design.
This TTL module can be used in counter and many of them can be cascaded to counts up to 99, 999,...
This circuit was obtained in an American publication of 1977. The circuit generates rectangular...
Epson SG 8018 Epson Crystal Programmable Oscillators Available from Mouser Electronics, these...