Actuating mechanisms light active

The use of two separate electrical or mechanical zones of detectors, both of which must be actuated before the confirmation of a fire or gas detection. For example, the detectors in one zone could all be placed on the north side of a protected area, and positioned to view the protected area looking south, while the detectors in the second zone would be located on the south side and positioned to view the northern area. Requiring both zones to be actuated reduces the probability of a false alarm activated by a false alarm source such as welding operations, from either the north or the south outside the protected area. However this method is not effective if the zone facing away from the source, sees the radiation. Another method of cross zoning is to have one set of detectors cover the area to be protected and another set located to face away from the protected area to intercept external sources of nuisance UV. If welding or lighting should occur outside the protected area, activation of the alarm for the protected area would be inhibited by second... 

Figure 6.19c shows a cross-sectional view of the lens cell in a flat state. The liquid was incompressible. When an external pressure was applied to deform the outer elastic rubber inward, the liquid in the lens chamber was redistributed, forcing the inner elastic membrane to swell outward. As shown in Figure 6.19d, the result was a planoconvex lens and the incident light could be focused. To activate the liquid lens, an electrically controlled actuator or mechanical lever could be employed. 

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