The continuity tester is a handy adjunct to an ohmmeter. The unit or
component whose continuity is to be checked is connected between
terminals E1 and E2 (which may be probes or croc clips). The test
current then flowing through the unit/component on test causes a
potential drop across resistor R2, which is applied to the non-inverting
input of buffer IC2. The output of the op amp is applied to transistor
T1, in the emitter circuit of which...
