The purpose of this circuit is to convert a short-lived pulse into a negative rectangular pulse. The circuit uses a unijunction that can be replaced by an equivalent such as 2N2646.
The circuit in the figure uses the four current amplifiers of the LM3900 to generate a sawtooth signal...
This circuit was found in an old Motorola documentation from the 70s, as it uses one of its...
This circuit for an optical audio link using LED or LASER was found in a 90s QST magazine. The circuit...