Found in an American publication from 1968, this circuit generates pulses at a rate of 2,500 per second. The transistor can be replaced by a modern equivalent.
This sensor circuit from a 1967 Ferranti documentation uses components from the era. The circuit...
This is the receiver for the previous circuit transmitter. Similarly, no information about the...
Found in a 90s Popular Electronics, this circuit uses two PLL tone recognizers to trigger by touch an...