We send the Non-invasive GEIPE Device with empty front-battery-compartment. To complete the circuit, “a clip with an attached wire, which is naked at the other end” is placed in that compartment as shown below. Thus the voltage will be around 3.0 volts due to the two standard AA alkaline batteries, like Duracell, placed in the back-battery-compartment. 

However, you can increase the voltage to 4.5 volts by moving the naked end of the wire so it is attached to the coils on the same side, and putting one AA battery on the other side, as shown below.

By removing the clip and its wire altogether, you can place two AA batteries in front compartment, making the total voltage around 6 volts (photo not shown).

Note: Other way to vary the voltage is to use rechargeable AA batteries which have close to 1.25 volts, so that use of one will reduce the current by at least 0.25 volts.