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- Aug 23, 2002
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I'll throw this out here as well based on the last information I have and how railroads work (class 1's).
I'll use the two big western ones as an example, and in general terms and not site specific.
BNSF's radio system is setup with with selective tower calling. Although a subdivision may run 400 miles onnhe same radio channel, based on RF progragation and terrain, BNSF assigns each radio tower a DTMF code. Once this code is heard, the tower will send out an acknowledgement tone and at the same time send an alert command to the dispatch center operator position. This will place a "call" indication on the tower that was alerted.
On the UP, same distance may be involved. However the UP uses a dispatcher DTMF code. When transmitting this code it is heard by all towers and a comparator votes on which tower is best receiving the transmission and routes that to the dispatcher as described above.
Currently there are no working products that work as a comparator on NXDN systems in this sense. Kenwood does have a system using the conventional IP network solutions but uses satellite recievers to accomplish this. However this is using a repeater operation and thus does not work in a railroad environment. This also does not help in the territories that use long Train repeater for train crews.
Now you also have the issue of alerting the dispatcher when you need to talk to them. How are going to properly selective call the correct tower and dispatcher? How many codes will be required and be acknowledged per site? The BNSF have multiple codes per tower depending if you want to talk to the dispatcher, help desk, police, etc.
To further expand that, you now have to deal with a dispatcher talking to one train and at the same time another train in the distance setting out a car. The dispatcher radio will wipe out and comms of that crew. Most rules require that work on the mainline remain on the road channel. With analog comms - although annoying a crew can still work around this. Digital it's all or nothing - so that doesn't really work either.
So moving along, you have trackside defect detectors (a lot of them) that would also need to be converted. Most modern ones use manufactured radios by the suppliers. No longer (in many cases) is a mobile radio just "plugged in" to the detectors. It's a custom built radio. So now you need to have them come up with a NXDN compatible radio at additional costs. Several railroad also employ a radio recall mode so if the train cannot hear the results the first time a DTMF sequence is used to get it to talk again.
Most railroads also employ radio power switches and derails in yards. Guess how they are controlled? DTMF - and many with long sequences. Several railroads also use these on main lines under TWC.
BNSF in Montana and Idaho still maintains legacy radio systems with telephone interconnect. How will that be intergrated in?
In a simplex operation, there is presently no good solution to replace simplex voice communications in a wide area operation. In order to do this, you'd be looking at the nations largest private SMR by area and users. That comes with a tremendous cost - with presently no good solution.
These are issues that came up in committee that were not completely explored. Everyone jumped on the digital bandwagon without figuring out how it will actually work out.
There are people working on it, but no viable solution has been developed by the manufactures and nothing is on the horizon at the mkment - without completely reinventing the wheel.
I'll use the two big western ones as an example, and in general terms and not site specific.
BNSF's radio system is setup with with selective tower calling. Although a subdivision may run 400 miles onnhe same radio channel, based on RF progragation and terrain, BNSF assigns each radio tower a DTMF code. Once this code is heard, the tower will send out an acknowledgement tone and at the same time send an alert command to the dispatch center operator position. This will place a "call" indication on the tower that was alerted.
On the UP, same distance may be involved. However the UP uses a dispatcher DTMF code. When transmitting this code it is heard by all towers and a comparator votes on which tower is best receiving the transmission and routes that to the dispatcher as described above.
Currently there are no working products that work as a comparator on NXDN systems in this sense. Kenwood does have a system using the conventional IP network solutions but uses satellite recievers to accomplish this. However this is using a repeater operation and thus does not work in a railroad environment. This also does not help in the territories that use long Train repeater for train crews.
Now you also have the issue of alerting the dispatcher when you need to talk to them. How are going to properly selective call the correct tower and dispatcher? How many codes will be required and be acknowledged per site? The BNSF have multiple codes per tower depending if you want to talk to the dispatcher, help desk, police, etc.
To further expand that, you now have to deal with a dispatcher talking to one train and at the same time another train in the distance setting out a car. The dispatcher radio will wipe out and comms of that crew. Most rules require that work on the mainline remain on the road channel. With analog comms - although annoying a crew can still work around this. Digital it's all or nothing - so that doesn't really work either.
So moving along, you have trackside defect detectors (a lot of them) that would also need to be converted. Most modern ones use manufactured radios by the suppliers. No longer (in many cases) is a mobile radio just "plugged in" to the detectors. It's a custom built radio. So now you need to have them come up with a NXDN compatible radio at additional costs. Several railroad also employ a radio recall mode so if the train cannot hear the results the first time a DTMF sequence is used to get it to talk again.
Most railroads also employ radio power switches and derails in yards. Guess how they are controlled? DTMF - and many with long sequences. Several railroads also use these on main lines under TWC.
BNSF in Montana and Idaho still maintains legacy radio systems with telephone interconnect. How will that be intergrated in?
In a simplex operation, there is presently no good solution to replace simplex voice communications in a wide area operation. In order to do this, you'd be looking at the nations largest private SMR by area and users. That comes with a tremendous cost - with presently no good solution.
These are issues that came up in committee that were not completely explored. Everyone jumped on the digital bandwagon without figuring out how it will actually work out.
There are people working on it, but no viable solution has been developed by the manufactures and nothing is on the horizon at the mkment - without completely reinventing the wheel.
