Darlington circuit with diode on common pin

[shemo]

When a diode is Not conducting, does it considered as open circuit?

if it is, then on the above picture, there is diode on the common pin connected to 12V, and if it's not conducting(open circuit) then the 12V cannot reached to the other side or powering the circuit?

True?

 

[KlausST]

Hi

Afaik true.

 

[chuckey]

Its so the transistor has back emf protection when driving an inductance connected between its output and the common + line.
Frank