Found in American documentation from 1969, this circuit uses logic inverters to obtain sequences of 4 pulses. The circuit can be used as a shield.
This circuit is recommended for alarm systems since it has a good output stage. The circuit is...
) Suggested by Philips in a 1968 documentation this circuit has very high 10 ohm on-load voltage...
No information is given about the transformers in this circuit suggested by Motorola in a 1968...