This crystal configuration can be made with triggers of any logic. The frequency is given by the formula next to the diagram. This setting is specifically for TTL.
This circuit, which can be used as a shield or in other applications, can be found elsewhere on...
This isolation circuit for audio signals was found in the August 1992 issue of Radio Electronics...
This circuit with the operational amplifier CA3130 was found in a documentation from 1977. The...