EXOR mit NANDs

This four-channel switch is an excellent aid when comparing digital signals with an oscilloscope. In the version described here the switch works as a chopper. With a small addition it can also work in `alternate` mode. The chopper fre- quency is generated by a Schmitt trigger (Nl) connected as an oscillator. With the given component values the oscil- lator frequency is about 2.5 MHz. This means that the chopper cycle frequency will be around 600 kHz, for the four- channel version described here.