This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
Many times it is quite an advantage to have a lamp or group of lamps so connected that the current may be turned on or off by any one of a number of different switches. For example, the lights in a long hall or passage-way can be lighted or extinguished by operating a switch at either end of the hall; the lights in the upper and lower halls of a residence, turned on or off by operating a switch upstairs or downstairs as the case might demand; the lights in the garage, controlled by switches at both the inside and outside door, etc.
Ill: Fig. 1 Lamps Controlled from Two Switches
The method of connecting a number of lamps to a circuit so that they can be controlled from either of two switches is shown in Fig. 1. The switches, as illustrated in this drawing, are in such a position that the lamps will burn. If either of the switches be thrown to its other position (there are two positions for each switch), the circuit will be opened. The operation then of either switch will again close the circuit.
The method of connecting a number of lamps to a circuit so that they can be controlled by any number of switches is shown in Fig. 2. The switches are all in such a position that the lamps will burn. If any one of the switches be turned to its second position (all the switches have two positions), the circuit will be open. The dotted lines at switch C show the connections through switch C after it has been operated. Operating switch D then will again close the circuit, by using the dotted lines in switches C and D. The wiring for the control of lamps, as just indicated, must comply with the underwriters' requirements and also city requirements, if the work be done in a place having city regulations for electric wiring.
Ill: Fig.2 Lamps Controlled by Any Number of Switches
Wire netting may be cut by laying it on the side edge of a spade and striking it with a hammer.