Many advances in lighting and communications have occurred in the past few years. With the cost of energy rising daily and the demand for accurate and reliable communications, any system that provides a higher level of efficiency must be considered.
In this chapter we will discuss public address systems, interoffice communications, and the fundamentals of fiber-optic communication cables and components. This chapter also will cover area streetlighting, floodlighting, and security lighting.
The type of public address system that you will install, maintain, and troubleshoot is intended for installation in administrative and living quarter areas. This system will be used for general announcements, for indoor talk-back paging, and to entertain or address personnel.
A common system authorized by the General Services Administration consists of one 100-watt solid- state amplifier, four trumpet speakers with drivers, two paging speakers, one dynamic microphone with floor stand, and all accessory terminal fittings and hardware required to operate this system. The set will conform to the design and functional test requirements of Underwriters Laboratory (UL) 813 Standard and the wiring and design requirements of the National Fiie Protection Association (NFPA) 70.
Before you install a public address system, refer to the National Electrical Code (NEC) and the manufacturers' recommendations. Several factors must be met for the permanent or temporary installation of a public address (PA.) system.
We will discuss these factors for the installation of a public address system, consisting of an amplifier (console), speakers, and cable that are approved for this system.
The solid-state amplifier comes with an ac power cord that is terminated in a three-prong plug. The power cord must be plugged into a three-wire, 120-volt, 60- hertz grounded outlet. The cord will ground the amplifier and the auxiliary power receptacle. The auxiliary power receptacle is a three-wire grounded outlet that supplies power to accessory sound equipment. The receptacle will supply power only as long as the amplifier is connected to a 120-volt power source and turned on.
The amplifier will be internally wired with a circuit breaker for protection. If the breaker trips, turn off the amplifier and reset the circuit breaker. Turn on the amplifier, and, if the breaker trips again, do not attempt to reset it. A problem exists that you will need to investigate and correct.
Figure 6-1. - Total speaker impedance matches the output impedance of the amplifier.Continue Reading