Aren’t cameras with VMD software examples of visual sensors?
No. Cameras are feature-rich products that need to be specifically selected, configured, and operated for particular use. This ongoing work adds lifecycle support costs to a site system that may make the “cure” (an intrusion notification system) more expensive the “disease” (intermittent copper theft, for example). In addition, the VMD software in brand-name cameras is simplistic: anyone who has spent hours attempting to tune VMD software for reliable outdoor detection - and then experienced hundreds of false positives - knows the frustration of this effort.
Cameras with more advanced analytic software on-board are better at reducing false positives; however, they are relatively expensive , require constant tuning by experts, and usually output high-bandwidth streaming media which cannot run over the low-speed/high-latency networks (cellular, satellite, DSL) available at most remote sites.