In this circuit of an old American documentation, the input impedance is the same as the output impedance. The circuit has a sensitivity of 1 Vpp at 75 ohms.
This Schmitt trigger in current mode for frequencies up to 50 MHz was found in a 1969 Motorola manual....
VR can be from 50 to 220k it is recommended to connect a 100-ohm resistor in series. The lamp may...
This circuit was published in a 1977 English magazine, but remains current, since we can assemble it...