ATC & Running Rails

I have a few questions regarding the ATC and running rails:

How does the ATC information run through the running rails? Is there a wire attached to the rail?

How does the car pick up the signal?

Where does the information come from?

Thank you...

ATC is equipment on the train, the Cab signal is what gives the indication thru a signal in rail.
yes there are wires attached to rail and many points, return current for traction, signal input etc.
The Cab signal sends code into a signal block varying at 0-60- 120-180 cycles, as soon as a train enters the block the wheels loop this signal between the two running rails.
Just in front of first Axle is two bars with coiuls on them that recieve the code thru induction. the different codes represent restricing, medium, limited, clear indications on the train display.
On the train the ATC equipment only translates the signals as right speed (or below speed) or as going to fast.
If going to fast the Engineer has 6 seconds to put brakes on and start to reduce the speed to where a right speed or below speed condition exists.
Im sure Phil Nasadowsi will translate this simplified explanation into a 200 page manual for the Techno geeks.

So, is the ATC/ASC system divided up into blocks the same way the fixed signal blocks are broken up? Or, is it based on the distance between your train and the train ahead of you? For example, If you're approaching a train that's stopped up ahead (and I know these aren't accurate numbers, I'm just using it to try and go through my example lol) say 5000 Ft and will display 80, then drop to 70 at 4000 ft, and drop to 60 at 3500 ft etc etc?

It works with ordinairy signal blocks.

ATC = Automatic Train Control, which usually involves moving blocks and computers to calculate the safe braking distance, although there are many different systems out there.

ATS = Automatic Train Stop, usually used in conjunction with a cab signal system, or trip cocks.

CSS = Cab Signal System, where the track communicates status information to the train cab. It can be used with fixed block systems and can enforce speed restrictions, depending on the system used. Some use trackside transponders, others use a signal transmitted through the rails.

I'm afraid this can all be confusing if you don't keep your terms straight.

(and I know these aren't accurate numbers, I'm just using it to try and go through my example lol) say 5000 Ft and will display 80, then drop to 70 at 4000 ft, and drop to 60 at 3500 ft etc etc?

you seem to have the right concept just stop thinking in feet.
It goes block to block usually three blocks sometimes four and also tied into the interlocking signals
EX If you enter a block and there is a train three blocks away you will get coded down to a 60
if there is a train two blocks away a 40 code
and if you enter an occupied block a 15 code
you can see the circuits along the right of way if you ride the front or rear of the train two boxes in tandem about six to eight feet apart
the asc is also tied into the interlocking signals
EX clear MAS code
medium clear 40 code
restricting 15 code

my numbers are also not acurate just a description of the way the system works

The cab signal system developed by the Pennsylvania Railroad by Union Switch and Signal was a pulse code based system.

At the end of each block, where a wayside signal was usually located, a set of pulse code generators would be installed. They look like this:

http://acm.jhu.edu/~sthurmovik/Railpics ... erator.jpg

While there are many different signal aspects there are only 4 standard "speeds" in the PRR (and most other) rulebooks. These are NORMAL (MAS, on the LIRR this is 80), LIMITED (40-45), MEDIUM (30) and SLOW/RESTRICTED (15-20). Since there are only 4 standard "speeds" the PRR felt they could get away with having four cab signals. These are CLEAR, APPROACH LIMITED, APPROACH and RESTRICTING.

On the LIRR, not wanting to be totally conformist, they dispensed with the signal name and just gave the speeds, 80, 40(45?), 30 and 15. Associated with each cab signal aspect is a code which is determined by the rate of electrical pulses. These are in decending order 180, 120, 75 and 0. They are designed to avoid harmonics giving a false higher code. Later on, the LIRR again wanting to be different added pulse rates of 270(?) and 420(?) for cab speed codes of 50 and 60 mph. Both 50 and 60mph would still be associated with "CLEAR" wayside signals, just to provide safety where the MAS wasn't 80.

The way the system works is at each point where one would have wayside signals, ie the end/start of a track-circut based block, there would be installed a set of code generators. These generators would use relay logic to pump the appropiate code into the rails IN FRONT of the train. The code would be based on the state of the NEXT block the train would enter. If the train was comming up on a 15mph type signal (like stop and proceed) then the '30' code would be generated and sent to the train. If the signal was APPROACH a 'MAS' code would be generated and sent to the train through the running rails.

The use of the running rails and the the absence of a pulse code giving a 15mph (Restricted) cab signal made the system failsafe. If the rails were broken or shorted out by lets say another train in front of you, you would recieve no code and hense 15mph cab signal. This enables the first train in a block to get a 'MAS' or other non-15 code and have a train in the same block get no pulses which gives a 15mph cab signal. Single car trains may not "short" all of this pulse current so single car trains must be given absolute block protection to the rear (unless specially equipped with special axle contactors).

ATC = Automatic Train Control, which usually involves moving blocks and computers to calculate the safe braking distance, although there are many different systems out there.

ATS = Automatic Train Stop, usually used in conjunction with a cab signal system, or trip cocks.

CSS = Cab Signal System, where the track communicates status information to the train cab. It can be used with fixed block systems and can enforce speed restrictions, depending on the system used. Some use trackside transponders, others use a signal transmitted through the rails.

Unfortunately you haven't quite kept your terms straight either.

ATC = Any train speed control system based on block information.

ATS = Any system which warns a train of non-clear signals OR stops a train after passing a "STOP" type signal.

CSS = What you said.

ACS = LIRR branded CSS with ATC.

Jersey Mike,

No need for question marks next to the codes.
I mentioned to you some time ago that the codes were 180 - 270 - 420 - 120 - 75 - 50 and no code. You just refused to believe it, although I've been working on LIRR MU cars for 20 years now.
You'll be pleased to know that the 50 code has been dropped from the M-7 equipment, however.
The fact still remains that the M-1 and M-3 cars were equipped for six codes and seven aspects, as described above.


Tom

Fantastic, guys, and thanks to all of you. A little cut and paste and you could almost make a training doc out of this.

<I>I mentioned to you some time ago that the codes were 180 - 270 - 420 - 120 - 75 - 50 and no code. You just refused to believe it</i>

I only ever took issue with the 50/15 code and if a Railroad never implements the system is it really there? PATCO does make use of the 50 code as they have enforced absolute stop via cab signal.

Jersey Mike,

You are very knowledgeable in signal matters. In my own convoluted way, I am showing you respect by taking you to task for questioning about the 50 code. A person who is fanatical about a subject also usually wants to be completely accurate about it.
That's all. We're good.

Tom

Didn't the M-1s origionally have provisions for an enforced stop via the ASC, too?

Yes, that is why a 50/15 code was present in the spec.

Didn't the M-1s origionally have provisions for an enforced stop via the ASC, too?

Well, Phil, these explanations tend to get a little insane, but I know you can handle it!

The answer is: Only in ATO operating mode.
If you will recall this table from way back...

M-1 original ATC reference voltages

The inputted reference voltages are all negative voltages, except for the voltage associated with the ZSR (zero speed relay). Actual speed equivalent voltage is represented by a positive voltage. If the voltage that emerges from the summing junction of the reference voltage and actual speed equivalent voltage remains a negative voltage, you are not in an overspeed condition. When the output from that summing junction is a positive voltage, you are in an overspeed condition.
You can now see that a positive reference voltage input into the system will put the train in overspeed immediately, even if stopped. The output from the summing junction has to be a positive voltage with a positive reference voltage input.
When the train was indeed stopped, a No Motion Relay interlock would bypass the normal deceleration requirement and keep the train from dumping brake pipe.

When manually operating the Master Controller, additional relay logic did and still does loop a no code condition to energize the 15SR (speed relay) instead of the ZSR.
This gives you a reference voltage for 15 mph speed limit.
Since ATO has been permanently disabled, ZSR should never energize.

Tom