Pagers and cell phones fail and drop calls. Truck sirens do nothing to alert the volunteers who are at home or at work that there s a fire. The dispatcher can't go out and knock on everybody's door, or find everybody who is in the back yard without their pager. Fire sirens are admittedly a redundant system, but, for emergency services, redundancies are important protection. Even a system fault that impedes cell/radio or digital communications can cause the firefighters to miss being alerted. Are you willing to risk your family's safety because you hear an annoying sound a couple of times a day?