a c output plug 33 in the presently preferred embodiment the a c invertor module 31 is operative to output 120 volts a c at a modified sinewave generating 50 watts of continuous power the a c invertor module 31 may preferably be provided with internal overload prior art polarity and short protection toggle switch 35 is operative to activate the a c invertor modular 31 to generate an output at a c output plug 33 or wire connectors 45 47 as with power supply unit 11 the a c invertor modular 31 is preferably formed to have a male support bracket on one side and a female support bracket on the other side thus the a c invertor modular 31 may be mechanically and electrically coupled to the power supply unit 11 in such a manner to oppose lateral separation of the power supply unit 11 and a c invertor modular 31 thereby ensuring electrical communication therebetween fig3 illustrates connection of the power supply unit 11 to a variable d c supply module 41 the variable d c supply module 41 is again formed to incorporate a male mounting bracket 43 on one side and a female mounting bracket not shown on the opposite side the variable d c supply module 41 is operative to receive power from the power supply module at its operating voltage level e g 12 volts d c and to convert that power level to a plurality of alternate d c voltage levels e g 1 5 volts 3 volts 4 5 volts 6 volts 7 5 volts 9 volts 10 5 volts and 12 volts the particular voltage.