- Joined
- Aug 23, 2002
- Messages
- 3,620
So, every so often this comes up.
Here is a quick lesson on what is going on.
Back in the day, the AAR was looking for a standard digital format when public safety went out with the P25 standard for voice communication.
The players for PS were essentially Motorola with their digital CODEC and DVSI with the IMBE CODEC. After some time, APCO decided on IMBE as the standard.
Sometime after, and with the narrowbanding coming, AAR did the same thing. The players were Motorola and "everyone else". Motorola had a good business with the railroads for decades. The "clean cab" standard that Motorola made radios of for the locomotives - was pure gold.
When the digital standard for AAR was looming, again Motorola and "everyone else" submitted their products. P25 based for Motorola and what would become NXDN/IDAS from those guys. However, Motorola also wanted a commitment from the industry for x amount of radios per year purchased to make it worth their while. At several thousand dollars a unit, the industry gave them a big FU.
I do not know the details of the selection, but the NXDN codec was chosen.
For awhile, the AAR stated that communications would be in the NXDN format. However, the techo geeks never really bothered to talk to the railroads.
Many, if not most field equipment is operated or responds to DTMF commands and/or PL tones. Dispatcher radios, remote switches, derails, trackside detectors and countless other pieces of equipment.
NXDN and DTMF are mutually exclusive, and replacing millions of dollars of wayside equipment just isn't going to happen. Not even in the long term. Due to the nature of how things actually work on the railroad, there just isn't anything that compares to what analog/signally does.
AAR backed off on the "requirement" years back, but in the railfan/scanner community they believe that its still there. There is nothing to *prevent* its use, but its *not* required. Its *only* required at interchange locations *if* digital voice is to be used between two different railroads.
Unless agreed upon and equipped, the AAR plan is to be used.
Some smaller railroads use it, some regionals ones do. I also am personally aware of some regional ones using commercial trunked systems - and that's ok. However when interchanging, they will use standard AAR channels.
There are many, many locomotives out there that do not have NXDN cab radios. Railroads do not assign the general pool locomotives by the radio capability. In fact, most locomotive radios are not tracked to the units so it could have one, one day, but then removed and placed into another one the next. They are designed to be easily replaceable.
Eventually they will be replaced one way or another, but that's the easy part.
Here is a quick lesson on what is going on.
Back in the day, the AAR was looking for a standard digital format when public safety went out with the P25 standard for voice communication.
The players for PS were essentially Motorola with their digital CODEC and DVSI with the IMBE CODEC. After some time, APCO decided on IMBE as the standard.
Sometime after, and with the narrowbanding coming, AAR did the same thing. The players were Motorola and "everyone else". Motorola had a good business with the railroads for decades. The "clean cab" standard that Motorola made radios of for the locomotives - was pure gold.
When the digital standard for AAR was looming, again Motorola and "everyone else" submitted their products. P25 based for Motorola and what would become NXDN/IDAS from those guys. However, Motorola also wanted a commitment from the industry for x amount of radios per year purchased to make it worth their while. At several thousand dollars a unit, the industry gave them a big FU.
I do not know the details of the selection, but the NXDN codec was chosen.
For awhile, the AAR stated that communications would be in the NXDN format. However, the techo geeks never really bothered to talk to the railroads.
Many, if not most field equipment is operated or responds to DTMF commands and/or PL tones. Dispatcher radios, remote switches, derails, trackside detectors and countless other pieces of equipment.
NXDN and DTMF are mutually exclusive, and replacing millions of dollars of wayside equipment just isn't going to happen. Not even in the long term. Due to the nature of how things actually work on the railroad, there just isn't anything that compares to what analog/signally does.
AAR backed off on the "requirement" years back, but in the railfan/scanner community they believe that its still there. There is nothing to *prevent* its use, but its *not* required. Its *only* required at interchange locations *if* digital voice is to be used between two different railroads.
Unless agreed upon and equipped, the AAR plan is to be used.
Some smaller railroads use it, some regionals ones do. I also am personally aware of some regional ones using commercial trunked systems - and that's ok. However when interchanging, they will use standard AAR channels.
There are many, many locomotives out there that do not have NXDN cab radios. Railroads do not assign the general pool locomotives by the radio capability. In fact, most locomotive radios are not tracked to the units so it could have one, one day, but then removed and placed into another one the next. They are designed to be easily replaceable.
Eventually they will be replaced one way or another, but that's the easy part.