A = regulator 7809, or 7806, or 7805, which respectively delivers 9V, 6V, ou 5V.

When combining the two resistances, the tension can be very precisely adjusted.


  Get an old camcorder, out of order, but with viewer still working.
identify the connections:
Open it, and give access to the connecting wires of the viewer. Disconnect each wire one by one, and each time, put the camcorder on, and check the action on the viewer. Thus, identify the "plus", minus" or ground, and video signal connections.
Other connections may be used for incrustations, led alarm, etc...
When one of the + or - wire is disconnected, the viewer is entirely off. When the video signal is disconnected, there is no image and the viewer is still lightened; however, on some, the viewer stops when there is no signal.
With a control device, check the polarity + and - directly on the camcorder connectors and measure the voltage value.
Electric feeding for viewer:
The feeding voltage of the viewer must be precise to 0.1V. Such module is easy to make. When modifying one or other resistance, the voltage can be exactly set:
With R1 = 0, the tension is 9, 6, or 5V related to the regulator; and with R2 very great, the tension is the primary one, e.g. 9,6, or 5V
With R2 between 0 et 10 ohms, the tension may go down to 1 V.