The proposed scheme allows for switching 12-volt electromagnetic relay from the source of voltage is halved.
In the initial state, T1 and T2 are closed, C1 is charged to a voltage of 6 In the chain R3 Is C1-D2. With the advent of the governing potential of T1 is opened, connecting positive plate of C1 to the common wire and simultaneously opening the transistor T2, which connects the upper circuit output relay bus +6 V.
Thus the relay is to discharge C1 under 12 V triggers, and after discharge C1 voltage 6 V, which, however; enough to sustain it in this state.
Author: R. Graham