guide, the system designer should be able to configure the proper system
control components for alarm assessment. Switchers are available from
several manufacturers with the capabilities required. Maximum camera
capacity varies from eight to 64 cameras. The various models available
provide for modular expansion to meet future needs. Once again, life cycle
cost analysis will determine which approach to take - purchase of a "large"
capacity system or multiple units, each with a smaller capacity. This
factor must be considered with the other considerations discussed in this
section. Figure 7, Section 2, depicts the various elements which the
designer can consider, some of which are discussed below and in Section 7.
Only after consideration of the full range of options, however, can the
security system designer properly design the IDS assessment subsystem.
6.2.5 The Role of Lighting in CCTV Effectiveness. The design of lighting
systems is not within the scope of this design manual. The brief discussion
herein is only intended to identify for the CCTV subsystem designer the
lighting factors which should be considered in the assessment subsystem
design. An excellent detailed treatment of security lighting design
guidance is contained in the Lighting Study for CCTV at Naval Security Group
Sites, published by the Atlantic Division, Naval Facilities Engineering
Command in June 1983. Key application considerations for the designer are:
a) Lighting improvements have proven more cost-effective generally
in security system design than expensive investments in very low light level
b) The type of lighting selected depends upon several factors. The
optimum light range of various camera types is often a significant factor.
Figure 39 provides a graphic representation of the relationships involved
between camera vidicons and various artificial and natural lighting sources.
c) Lighting has a deterrent effect. The purpose of most lighting
upgrades is (or should be) to eliminate places of concealment.
d) For CCTV applications, good contrast is most important for
intruder presence determination under marginal lighting conditions. New
techniques such as the use of retroreflective materials in clear zones
should be considered, as should the fact that low pressure sodium lighting
provides poor contrast.
e) The designer should keep in mind that fluorescent lighting, the
most common DoD and Navy interior lighting source, is a source of nuisance
alarms to some sensors (see Section 4, paragraph entitled "Volumetric
Sensors-Interior"). A trade-off may have to be made between IDS element
selection and performance and lighting type selection.