Electrical Estimating Methods, 4th Edition

CHAPTER 20 Special Systems

SPECIAL SYSTEMS

Special systems include unique control or monitoring equipment used for specialized applications in residential, commercial, and industrial construction. Included in this chapter are sections ranging from electric heating and residential wiring to communication, public address, and sound systems. Doorbell and hospital paging systems are also covered. Each of these items is first described, then given appropriate units for measure, along with material and labor requirements and instructions for the takeoff procedure.

CLOCK SYSTEMS

A variety of clock systems are available. The most common types have a master clock, a tone generator and control, an antenna, a lightning arrester, and slave clocks. The system picks up radio signals every hour from the National Bureau of Standards to keep the master clock set at the correct time. In turn, high-frequency tone signals are sent out over the regular receptacle wiring to keep the system's clocks on time. In this type of system, the clocks are plugged into the regular receptacle.

Other systems use different methods of resetting clocks. Some have two-motor clocks, with a control that speeds up the clock with the second motor. These systems require separate conduit and an independent wire system. Program signaling is also controlled through the master clock and controller.

Another option, a combination clock and speaker, consists of a back or rough-in box, trim, and grille for the speaker and ...