End mishaps in the dark; with switches at both ends of a hall,  lights are controlled as desired.

The secret of two-way control lies in the three-wire connecting cable and three-terminal switches, as shown.

IN MANY houses, the switch controlling an important light in a long hallway or over the cellar stairs is in the right location only if approached from one direction. If you approach from the other direction when the house is dark, you have to fumble around and perhaps light a match to find it.

If you are afflicted with such an arrangement, you can improve it if you can conveniently snake an additional piece of three-wire cable through the walls from the present switch box to a new box at the other end of the passageway. You must discard the existing single-pole (two-terminal) switch, and install two new switches known as "three-way" switches. (This is a puzzling misnomer, as they provide only two-way control.) They are of the single-pole, double-throw type, have three terminal screws (which is probably how they got their name), and fit standard wall boxes.

For purposes of identification, the wires in the three-wire cable are colored white, black and red. The switches are mounted in the boxes with the single terminal screws toward the top.

Caution: Before opening the present switch box, kill the circuit by removing the appropriate fuse or tripping the circuit breaker. Have a flashlight handy for illumination.

The accompanying picture diagram shows the hook-up. Note that the white wire (the grounded side of the power line) is carried through without break to the lamp socket. The black wire is cut at both boxes for connection to the side terminals of the switches. The red wire connects only to the single side terminals of the switches. Either switch turns the light on or off. "On" can be either the up or the down movement of the switch arm, depending on the position of the other switch arm. The arrangement is very convenient, and saves many an accidental tumble over a roller skate or a baseball. ·

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