The circuit is from 1994 National Semiconductor documentation. The component is not easy to obtain, but there are equivalents that can be searched.
This circuit can be used with the CIR12053 receiver or with others shown in this section of the...
When the input of this circuit goes to high level, the LEDs start to flash alternately. The...
This circuit is from a 1965 Radio Electronics. The triggering transformer generates high voltage...