Astrak wrote:
Normally the PRO-97 will not display a tone until it picks it up in search mode, it doesn't scroll through them.
Maybe you're a little confused, or maybe I'm a little confused here.....:wink:
Like I said before I'm not familiar with the PRO-97 but in your original post you said that the CTCSS constantly changes while you're listening to a transmission and that the radio is in the CT search mode. If you can see the CTCSS tone constantly changing, and you know the radio is in the CTCSS search mode then one way to describe what you're seeing on the radio display could be called scrolling.
Anyway, to answer your railroad radio question.......rail radio works just the same as any other basic two-way radio system. I dispatched for a large northeastern commuter railroad. My territory consisted of 90 miles of double-track railroad hosting both our commuter trains and freight trains of a major freight railroad. We used one frequency for the entire territory and selected the repeater/antenna sites based on where the train was we needed to talk to. In the field the engineer or conductor would key up and the signal was automatically picked up by the nearest repeater/antenna. This allowed us to talk to multiple trains, on the same frequency, at the same time, without interfering with anyone else on the same frequency. In my opinion this was not the best arrangement since there were several territories that all used this same frequency. The southern half of the the state had a different frequency, but it was the same method.
I have family in Omaha, NE and I've listened to both the UP and the BNSF railroads when I'm visiting. I've heard those same tones before and after transmissions and after talking to other train dispatchers, radio people, and rail buffs I've found out that those tones are either DTMF (Dual Tone Multi-Frequency) or PBX (Private Branch Exchange) tones. These tones are used to activate specific repeater/antenna sites. Again, this allows trains on the same frequency to talk to different dispatchers without interfering with each other. It works much the same as CTCSS or DPL, the only difference, from a scanner standpoint, is that all you need to do is program the radio frequency in and listen.
Hope this helps......and of course if anyone can correct/update my information I'd be more than grateful!