Building Design and Construction Handbook - Merritt - Ventech!

ELECTRICAL SYSTEMS 15.75
exchange (CBX), or switch, that controls the telephone system functions. It can
offer numerous desirable features such as direct inward dialing, voice mail, speed
dialing, system forward, conference, forward, message waiting, queuing, and transfer.
The switch is located in a telephone service closet and requires power (preferably
conditioned power) and air conditioning.
Telephone service is distributed via cables in conduit extending from telephone
service room to telephone closets on each floor. Each closet should have a plywood
backboard, for mounting equipment and punch-down boards, and two duplex receptacles.
For distribution of telephone cables to their point of use, ladder-type
cable trays can be routed above corridor ceilings from the telephone closets
throughout each floor. Telephone cables must be suitable for running in cable trays
and must be rated for use in air-handling spaces.
Telephone outlets consist of a single-gang outlet box with stainless steel cover
plate, modular phone jack, and 3 ⁄4 in electrical metallic tubing, which is run concealed
to the cable tray. Telephones may be digital electronic type with programmable
function buttons in addition to the 12-button tone pad, plus speaker phone
and intercom features.
15.19.4 Intercom and Paging Systems
Intercom can be an integral function of the telephone system or a separate system.
Many buildings have a paging system of some sort. This can be a telephone
system function, but it is most often a separate system consisting of receivers,
playback equipment, amplifiers, speakers, telephone interface, and a microphone.
The system may offer selective paging of certain areas, all-call paging of the entire
facility, and background music.
15.19.5 Security Systems
These can range in sophistication from a combination lock (pad of numbered push
buttons) or a simple card reader at the entry door to a comprehensive system integrating
physical barriers, electronic access controls, surveillance, and intrusion
detection systems (IDS). Although a card reader usually suffices for access control,
high-value and high-security facilities often require biometric identification systems,
such as retinal scan or hand geometry, for control of access.
Intrusion detection systems usually are of either of two types. One is a perimeter
system, such as door switches, break-glass detectors, optical, or microwave beams,
which creates an electronic envelope around a space. The other is a volumetric
system, passive infrared or ultrasonic, which detects an intruder’s presence in the
protected space.
Closed-circuit television (CCTV) cameras may be provided to allow security
persons to continuously watch for intruders at any of many locations from one
point. Since several cameras may be required, video sequencers are provided that
display the images from each of the cameras in turn on one or more monitors.
Sequencers may be connected to the IDS to display and hold the image from a
camera located where an alarm occurs.
A central security computer controls all of the security system functions. It
monitors all of the devices and wiring, presents trouble and alarm messages to
security staff, and keeps a historical record of all events such as authorized entries
and alarms.