The Motorola Minitor is a portable, analog, receive only, voice pager typically carried by fire, rescue, and EMS personnel (both volunteer and career) to alert of emergencies. The Minitor, slightly smaller than a pack of cigarettes, is carried on a person and usually left in selective call mode. When the unit is activated, the pager sounds a tone alert, followed by an announcement from a dispatcher alerting the user of a situation. After activation, the pager remains in monitor mode much like a scanner, and monitors transmissions on that channel until the unit is reset back into selective call mode either manually, or automatically after a set period of time, depending on programming.
Purpose and History
In the times before modern radio communications, it was difficult for emergency services such as volunteer fire departments to alert their members to an emergency, since the members were not based at the station. The earliest methods of sounding an alarm would typically be by ringing a bell either at the fire station or the local church. As electricity became available, most fire departments used fire sirens or whistles to summon volunteers (many fire departments still use outdoor sirens and horns along with pagers to alert volunteers). Other methods included specialized phones placed inside the volunteer firefighter's home or business or by base radios or scanners. "Plectron" radio receivers were very popular, but were limited to 120VAC or 12VDC operation, limiting their use to a house/building or mounted in a vehicle. There was a great need and desire for a portable radio small enough to be worn by a person and only activated when needed. Thus, Motorola answered this call in the 1970s and released the very first Minitor pager.
There are six versions of Minitor pagers. The first was the original Minitor, followed by the Minitor II(1992), Minitor III(1999), Minitor IV, and the Minitor V released in late 2005. The Minitor VI was released in early 2014. The Minitor III, IV, and V used the same basic design, while the original Minitor and Minitor II use their own rectangular proprietary case design. Similar voice pagers released by Motorola were the Keynote and Director pagers. They were essentially stripped down versions of the Minitor and never gained widespread use, though the Keynotes were much more common in Europe because they could decode 5/6 tone alert patterns in addition to the more popular two tone sequential used in the United States.
Although the Minitor is primarily used by emergency personnel, other agencies such as utilities and private contractors also use the pager. Unlike conventional alphanumeric pagers and cell phones, Minitors are operated on an RF network that is generally restricted to a particular agency in a given geographical area. The Minitor is the most common voice pager used by emergency services in the United States. However, digital 2-way pagers that can display alpha-numeric characters can overcome some of the limitations of voice only pagers, are now starting to replace the Minitor pagers in certain applications.
Activation
Minitor pagers, depending on the model and application, can operate in the VHF Low Band, VHF High Band, and UHF frequency ranges. They are alerted by using two-tone sequential Selective calling, generally following the Motorola Quick Call II standard. In other words, the pager will activate when a particular series of audible tones are sent over the frequency (commonly referred to as a "page") the pager is set to. For example, if a Minitor is programmed on VHF frequency channel 155.295 MHz and set to alert for 879 Hz & 358.6 Hz, it will disregard any other tone sequences transmitted on that frequency, only alerting when the proper sequence has been received. The pager may be reset back into its selective call mode by pressing the reset button, or it can be programmed to reset back into selective call mode automatically after a predetermined amount of time, to conserve battery power.
Older Minitor pagers (both the Minitor I and Minitor II series) have tone reeds or filters that are tuned to a specific audible tone frequency, and must physically be replaced if alert tones are changed. For two-tone sequential paging, there are two reeds, the first tone passes through the first reed, and the second tone passes through the second reed, thereby activating the pager. Beginning with the Minitor III series, these physical reeds or filters are no longer necessary, as the pagers now feature all solid-state electronics, and various tone sequences can be programmed via computer software.