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78 RICHARDSON'S BLUEBOOK OF PROJECTION
Switch Location
The location of switches deserves careful attention. (60) First of all, under no circumstances should the emergency light switches be located on the main switch board. In case of fire an excited employee might pull this switch and plunge the entire theatre in darkness.
(61) It is best to place emergency light switches in a locked box in the manager's office or in the box office where no one can get at them except the ticket seller and manager. The key to the box should be left attached to the box door. In the projection room local conditions will of course govern the location of the switches, but convenient accessibility should be the governing factor.
Careful About S. P. Switches
(62) Before installing a single pole switch be sure its use is not prohibited by Underwriters' or local regulations.
DPST switches ordinarily are used to control all incandescent, motor and projection circuits, except those on which DPDT or TPDT switches are required. TPDT switches are used for all 3-wire circuits. Generally the type of switch called for depends upon (a) the work it will have to do and (b) restrictions imposed by Underwriters' rules.
Switch Markings
(63) The National Electric Code requires that switches have certain dimensions, according to the voltage of the circuit they are connected to and the amperage they must carry. Both the voltage and amperage capacity must be stamped upon some part of every switch. Reject any switch not so marked.
A switch may be used for a circuit of any voltage less than it is marked for, or for any amperage less than its rating. (64) No switch may be used for a higher voltage or amperage than it is marked for. 250-volt switches are used in theatres almost universally. There is no switch made that is marked for 110 volts, the requirements for 110 and 220 volts being identical.