Motorola Minitors

[ffdave77]

I am a VF and I was wondering how the Minitor works. Does the minitor recognize the tone by pitch or is there a set a numbers transmitted through the tone? Always have been a question in my mind.

I once saw a video of a fire department who called for mutual aid, and when the tone went off for that department, it activated the garage door and injured a firefighter. Just an interesting thought.

 

[N_Jay]

I am a VF and I was wondering how the Minitor works. Does the minitor recognize the tone by pitch or is there a set a numbers transmitted through the tone? Always have been a question in my mind.

I once saw a video of a fire department who called for mutual aid, and when the tone went off for that department, it activated the garage door and injured a firefighter. Just an interesting thought.

Most systems use two-tone sequential signalling.
There are numerious pairs of tones to signal specific pagers or groups of pagers. The system also contains a "long tone B" code which can activate larger groups.
Some pagers respond only to thier tone set, others to their tone set and "long B", others to several tone sets.

The fire house door was probably hooked to a receiver to open it automatically when the station was toned-out. My guess is it was wired by an "expert" who did not consider that a second alert would close the door.

 

[thumbtrap]

Some good information on the various minitors and their options/alert system is available at http://www.batlabs.com/minitor.html .

As far as I know, the alert tones are only transmitted as audible tones - if you put your pager in monitor mode for a while you will hear the tones as they alert various other stations. If your station is alerted, it will still beep at you - no worries - in fact, you may have a few seconds lead time. Our dispatch often will say Station xyz, breathing difficulties, vague street (no address) - and then pause for a second or two. (I supposed while they key something in or look stuff up or alert EMS) then the alert tones come on and they repeat the dispatch, this time with actual useful information about the location and more detailed information.

Your system may be cross patched on multiple frequencies - most likely because they still have old pagers floating around. (So just because you hear familiar station numbers doesn't necessarily mean you found it.) These other frequencies may be for other systems and may work differently. Ours goes out VHF low band, UHF, and on the 800mhz trunked system. They all seem to carry the alert tones. Look at the back of your minitor for the frequency and try that on your scanner.(Mine is incorrect, but the band is right.) Most any scanner will pick up all three bands that minitors are available in.

Forget the garage door - all I want is a lapel beeper so I can hear the alert tones for certain on the lawn mower.

 

[Hoseman292]

Pager Theory of operation

Basically in the Motorola Pageboy, PageboyII, PageboyIII, Minitor, and the MinitorII, the pager has two boards installed within the housing. One board is the radio while the other is the decoder. On the decoder board there are what is called "Vibrasponders, reeds, or active filters".

The pair of tones (first tone then second tone) is generated through the dispatch center. It is then recieved through your pager. The reeds or active filters determine which pitch is correct (by means of small tuning forks vibrating within them) and triggers the decoder circuit to sound the familiar intermittant beep which you are accustomed to hearing when your company gets a call.

There are many different avenues of paging as well as receivers designed to work with various types of these systems. Some receivers are stationary which use the same concept but instead of sounding a beep tone, they close relay circuits which in fire stations, turn on lights, open apparatus doors, sound bells and buzzers, or even change traffic lights.

I once heard that in some rural places where there are tornado warnings, there are facilities that send paging tones that are then recieved by a tone alert receiver which then makes a relay closure to start a gasoline generator which then powers an air raid siren to warn the citizens of a possible tornado condition. Talk about a chain of events!

Regards,
Timothy Bell - N3WIR
Firefighter Montgomery County DFRS
Former Fire Dept. Dispatcher MCDFRS