neutral conductor 107 connectable to a mating socket arranged to receive the conductors 105 107 the disc 104 rotates peripheral keys 109 112 and a switch 113 when an operator turns a screwdriver slot 108 or otherwise grasps and turns the disc 104 one of keys 109 112 locks into position adjacent the receptacle 103 to mate with one socket and bar others for example in the position shown in fig1 b a socket designed for a 105 vac power supply mates with key 109 additional power supply values appear on the view of disc 104 in fig1 c fig1 d which is section 1d through fig1 c shows how disc 104 rotation operates rotary switch 113 a shaft 114 connects disc 104 to switch rotor 117 which completes contacts in a well known manner as it steps through positions held by a ball detent 115 and spring 116 fig2 illustrates an electrical device 101 carrying an electrical connector 102 receptacle 103 receives a mating keyed socket 202 connected to a wall plug 203 via a line cord 204 of a line cord set 201 receptacle 103 also connects to output cable 205 and output socket 206 through rotary switch 113 an output plug 207 is inserted into output socket 206 to ultimately connect cable 208 and utilization circuit 209 to power supply voltage at wall plug 203 the actual voltage applied to the utilization circuit 209 depends upon the position of disc 104 and the mating keyed socket 202 on line cord set 201 the receptacle 103 and disc 104 in fig3 are arranged to receive a mating keyed socket 202 connected to a 115 vac wall plug 203 as shown in fig5 rotation of the disc 104 two steps in either direction rearranges the receptacle to.