lagasse@biomed.UUCP (Robert C. Lagasse) (07/03/85)
Living around Boston, I have heard several walkie-talkies that the transit police carry and also the EMS ambulance people. They all seem to be Motorolas. Anyway, it seems that when the base station releases its mike key, a couple of single tones are transmitted, very rapidly, one after another, each about 100mS long, with no space in between them, the first tone higher in freq than the other. One is about 1.5kHz and the other a bit lower, maybe around 1kHz. WHAT are these for? All comments appreciated. N 1 A L G Bobby L.
ron@brl-tgr.ARPA (Ron Natalie <ron>) (07/05/85)
> > Living around Boston, I have heard several walkie-talkies that the > transit police carry and also the EMS ambulance people. They all seem to be > Motorolas. Anyway, it seems that when the base station releases its mike > key, a couple of single tones are transmitted, very rapidly, one after > another, each about 100mS long, with no space in between them, the first > tone higher in freq than the other. One is about 1.5kHz and the other a bit > lower, maybe around 1kHz. WHAT are these for? > Baltimore City has the{k bleedles. They are a data burst. They transmit call information to the stations and engines. The officer in the engine just pushes the buttons to indicate the situation on arrival at the scene. I think the trade name is something like MODAC. -Ron
parnass@ihu1h.UUCP (Bob Parnass, AJ9S) (07/06/85)
> Living around Boston, I have heard several walkie-talkies that the > transit police carry and also the EMS ambulance people. They all seem to be > Motorolas. Anyway, it seems that when the base station releases its mike > key, a couple of single tones are transmitted, very rapidly, one after > another, each about 100mS long, with no space in between them, the first > tone higher in freq than the other. One is about 1.5kHz and the other a bit > lower, maybe around 1kHz. WHAT are these for? > > All comments appreciated. > N 1 A L G Bobby L. I think what you heard are the tone signals generated by the remote control unit located at the base operator position. This control unit is probably connected via dedicated "phone" lines to the actual transmitter. Since these "phone" lines have no DC continuity, tone signals are used to remotely control the transmitter (e.g. transmit, receive, change channel, etc). Although these tones are supposed to be muted to prevent their transmission over the air, it's not uncommon to hear them "slip out". I hear these tones on the Bolingbrook (IL) Police base on 155.250 MHz, and the Illinois Department of Tran- sportation on 151.100 MHz. -- =============================================================================== Bob Parnass, Bell Telephone Laboratories - ihnp4!ihu1h!parnass - (312)979-5414