Passive infrared sensors at doorways protect fauna and flora displays at night. During the day, infrared sensors trip a relay to tally the number of visitors entering the Happy Isles Nature Center. Sensors monitor the operation of three sewage stations that pump water to a treatment plant outside the park. If a pump fails or the sewage level threatens to spill into the Merced River, detectors trip a digital dialer which alerts the dispatch center. Using underground cables that tabulate the number of cars entering the park, the system identifies congested areas. In a mile-long tunnel, equipment monitors hazardous air conditions. To protect visitors from hazardous areas, plans are underway to install fiber optic fence strands that sound a warning alarm when broken. The article describes improvements the electronics technican wants to make. Illustrative photographs.