by howardr142
What is the Zero Speed Relay? I remember seeing a override switch for this on the NJT ALP46s.
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Cab Signals
- Discussion of the past and present operations of the Long Island Rail Road.
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by DutchRailnut
The zero-speed or V-Zero relay does two things it protects the doors circuits from getting open signal while moving. and proves to event recorder if a locomotive was stopped.
If Conductors are in charge, why are they promoted to be Engineer???
Retired Triebfahrzeugführer. I am not a moderator.
Retired Triebfahrzeugführer. I am not a moderator.
by N340SG
That's correct. But, just to clarify a bit; On the M-1, the Velocity Zero function is called the "No Motion Relay". There is no Velocity Zero Relay per se on the M-1. The Zero Speed Relay is one of the relays that would respond (if it wasn't bypassed) to the code in the rails to enforce the respective speed command.
There were 2 vendors involved with the M-1 Speed Control system.
US&S did the Cab Signal part only. GE had the enforcement equipment.
So, with a 75 code in the rails, the US&S equipment would energize the "L" relay. That relay would interface with the GE package, energizing the 30SR, thereby enforcing a 30mph speed limit.
Likewise, the ZSR, when energized, would have enforced whatever speed limit was associated with it.
On the M-3 and M-7, US&S equipment does the entire job.
Tom
There were 2 vendors involved with the M-1 Speed Control system.
US&S did the Cab Signal part only. GE had the enforcement equipment.
So, with a 75 code in the rails, the US&S equipment would energize the "L" relay. That relay would interface with the GE package, energizing the 30SR, thereby enforcing a 30mph speed limit.
Likewise, the ZSR, when energized, would have enforced whatever speed limit was associated with it.
On the M-3 and M-7, US&S equipment does the entire job.
Tom
Last edited by N340SG on Mon May 17, 2004 1:02 pm, edited 1 time in total.
by howardr142
Ok, so the Zero-Speed relay does not allow the crew to operate the doors. Same as the No-Motion relay. The zero-speed, except on the M1/M3's cut power the Power throttle interlock so that the engineer cannot take power?
The door-bypass switch does the same thing?
If the VZR was overridden, then the speed code would not be enforce?
The door-bypass switch does the same thing?
If the VZR was overridden, then the speed code would not be enforce?
by howardr142
[quote]"The Zero Speed Relay is one of the relays that would respond (if it wasn't bypassed) to the code in the rails to enforce the respective speed command."[/quote]
So in that case what is use of cutting the ASC? Can't they just use the Zero speed relay?
So in that case what is use of cutting the ASC? Can't they just use the Zero speed relay?
by N340SG
howardr142,
I think it's just a matter of different companies at different eras using different nomenclature for equivalent system functions.
First, I don't know what the Zero Speed Relay is for on the NJT equipment you cited, or why there would be a bypass switch for it.
The terminology I used is for our LIRR cars only. There is probably no industry standard terminology for these things. It's whatever some designer dude decides to call a given function.
On the LIRR EMU cars, the Velocity Zero function is called exactly that on the M-3 and M-7 cars. On the M-1 cars, it is called "No Motion". It is the same idea, just different name. The main purpose of the ATC system declaring a state of zero velocity (or "no motion") is, as Dutch said, that we don't want the doors to be able to be opened unless the train is at rest, or at velocity zero.
On the OEM M-1 only, the Zero Speed Relay is the relay that would enforce whatever speed restriction was associated with a no code condition, be it 15, 10, 8, 5, or whatever mph it was set for. It's called the ZSR simply because that's what GE decided to call it. It should absolutely not be confused with the Velocity Zero function.
The LIRR is not using the ZSR, however. So, if it makes it easier, just forget about it. The circuit from a no code condition, that would normally energize the ZSR, is removed from the ZSR coil, and wired to the 15SR coil. So, a no code condition enfoces the 15 mph speed limit.
Door bypass is completely different, and actually has nothing to do with the ATC system. What normally occurs is a series circuit runs through interlocks on what's called SLRs (Signal Light Relays) in each car. SLRs are energized (fail safe design) when all doors are closed in a vestibule. The red lights in the vestibule area (inside and outside) that indicate one or more doors are open in that vestibule area should extinguish when the SLR energizes. That's why the trainmen will look out the window when the Engineer announces, "No door light." They're looking for a red light still lit, so they can go right to where the problem door is.
When all doors are closed, this series circuit runs through all the energized SLRs in the train, and energizes a relay, PIR (Power Interlock Relay), that is one of the required relays that must be energized to allow the Engineer to have the train draw power. The Engineer's "Doors Closed" light (or "Door Light") will illuminate when the PIR energizes.
If the train crew cannot get the red light to go out in the affected vestibule area, the train cannot draw power. So, it is necessary to flip the "Door Bypass" switch, which bypasses the door light circuit in the entire train, and hotwires the PIR. In bypassing this important safety feature, the crew has to be governed accordingly.
(Note that the M-7 has additional ways to ascertain what door(s) are problematic. And the basic PIR function in the M-7 is called TIR- Traction Interlock Relay. Same thing, only different.
)
I think it's just a matter of different companies at different eras using different nomenclature for equivalent system functions.
First, I don't know what the Zero Speed Relay is for on the NJT equipment you cited, or why there would be a bypass switch for it.
The terminology I used is for our LIRR cars only. There is probably no industry standard terminology for these things. It's whatever some designer dude decides to call a given function.
On the LIRR EMU cars, the Velocity Zero function is called exactly that on the M-3 and M-7 cars. On the M-1 cars, it is called "No Motion". It is the same idea, just different name. The main purpose of the ATC system declaring a state of zero velocity (or "no motion") is, as Dutch said, that we don't want the doors to be able to be opened unless the train is at rest, or at velocity zero.
On the OEM M-1 only, the Zero Speed Relay is the relay that would enforce whatever speed restriction was associated with a no code condition, be it 15, 10, 8, 5, or whatever mph it was set for. It's called the ZSR simply because that's what GE decided to call it. It should absolutely not be confused with the Velocity Zero function.
The LIRR is not using the ZSR, however. So, if it makes it easier, just forget about it. The circuit from a no code condition, that would normally energize the ZSR, is removed from the ZSR coil, and wired to the 15SR coil. So, a no code condition enfoces the 15 mph speed limit.
Door bypass is completely different, and actually has nothing to do with the ATC system. What normally occurs is a series circuit runs through interlocks on what's called SLRs (Signal Light Relays) in each car. SLRs are energized (fail safe design) when all doors are closed in a vestibule. The red lights in the vestibule area (inside and outside) that indicate one or more doors are open in that vestibule area should extinguish when the SLR energizes. That's why the trainmen will look out the window when the Engineer announces, "No door light." They're looking for a red light still lit, so they can go right to where the problem door is.
When all doors are closed, this series circuit runs through all the energized SLRs in the train, and energizes a relay, PIR (Power Interlock Relay), that is one of the required relays that must be energized to allow the Engineer to have the train draw power. The Engineer's "Doors Closed" light (or "Door Light") will illuminate when the PIR energizes.
If the train crew cannot get the red light to go out in the affected vestibule area, the train cannot draw power. So, it is necessary to flip the "Door Bypass" switch, which bypasses the door light circuit in the entire train, and hotwires the PIR. In bypassing this important safety feature, the crew has to be governed accordingly.
(Note that the M-7 has additional ways to ascertain what door(s) are problematic. And the basic PIR function in the M-7 is called TIR- Traction Interlock Relay. Same thing, only different.
)
by RC '75
Just a few questions:
How does a LIRR MU train get a specific ATC signal? Who and/or what determines how fast a train should be going? Does the engineer still determine the speed while ATC is on?
How does an engineer determine how slow or fast to go at a signal aspect? If a signal is "Medium Approach" must a train go an exact speed? Or can it travel within a speed zone?
Does ATC/ATO exist in the non-electrified areas?
Is there indeed a difference between ATC and ATO.
Thanks for all the info....
How does a LIRR MU train get a specific ATC signal? Who and/or what determines how fast a train should be going? Does the engineer still determine the speed while ATC is on?
How does an engineer determine how slow or fast to go at a signal aspect? If a signal is "Medium Approach" must a train go an exact speed? Or can it travel within a speed zone?
Does ATC/ATO exist in the non-electrified areas?
Is there indeed a difference between ATC and ATO.
Thanks for all the info....
by Jersey_Mike
How does a LIRR MU train get a specific ATC signal?Thre is an inductance based reciever suspended in front of the leading truck a few inches above the rail.
Who and/or what determines how fast a train should be going?The CSS speed is set in whatever ATC circutry there is.
Does the engineer still determine the speed while ATC is on?Yes, as long as it does not exceed the maximum speed allowed for the cab signal aspect.
How does an engineer determine how slow or fast to go at a signal aspect?With the LIAR ASC system the cab signals are displayed as speeds on the Cab Display Unit.
If a signal is "Medium Approach" must a train go an exact speed? Or can it travel within a speed zone?Approach Medium corresponds to a cab signal aspect of 40 or 45 mph, which the engineer then cannot exceed (+- a margin or error).
Is there indeed a difference between ATC and ATO.ATC is what is in use on the LIAR as well as all other cab signaled railroad lines and it involved the use of enforced speed limits and the engineer being peanalized for exceeding those limits. ATO means the engineer would only have to press START or STOP and the trains would operate autonimously in between. ATO is seen on such transit systems as the DC Metro and PATCO in philly.
by N340SG
RC '75,
ATO, as implemented on the M-1 cars, used the ATC apparatus to follow the current speed limit. It would not make station stop spots, or automatically open doors, or stuff like that. Only the LIRR M-1 cars had ATO installed. Subsequent EMU cars did not have the equipment installed. ATO has been abandoned on the LIRR for some time now.
Speed limits would be instituted due to a variety of things:
Block lengths, stopping distance, track curvature and other track geometry, etc.
If you mean how does the train know the current speed limit, the Cab Signal equipment picks up the desired speed code from the running rails, which is shunted by the first set of wheels in the train, so that only the track receivers in the controlling cab can receive the code.
In the ATC circuitry is a comparator circuit that takes the desired speed from the track code, and compares it to the actual speed, from speed sensors (transducers) mounted on the gearcases. If the train is going too fast for the current code, the brakes will automatically apply, slowing the train until the overspeed condition is cleared.
If the Engineer has an MAS (Maximum Authorized Speed - 80 MPH in LIRR EMU cars) code, he can physically do any speed from 0 - 80. If he goes above 80, the brakes will apply. That enforcement applies to any speed limit associated with whatever code is present in the rails. It cannot be exceeded.
The main beauty of the system is it is fail-safe. Track circuit failure, broken rail, etc, will produce the most restrictive code, I.E., no code.
Tom
ATO, as implemented on the M-1 cars, used the ATC apparatus to follow the current speed limit. It would not make station stop spots, or automatically open doors, or stuff like that. Only the LIRR M-1 cars had ATO installed. Subsequent EMU cars did not have the equipment installed. ATO has been abandoned on the LIRR for some time now.
Speed limits would be instituted due to a variety of things:
Block lengths, stopping distance, track curvature and other track geometry, etc.
If you mean how does the train know the current speed limit, the Cab Signal equipment picks up the desired speed code from the running rails, which is shunted by the first set of wheels in the train, so that only the track receivers in the controlling cab can receive the code.
In the ATC circuitry is a comparator circuit that takes the desired speed from the track code, and compares it to the actual speed, from speed sensors (transducers) mounted on the gearcases. If the train is going too fast for the current code, the brakes will automatically apply, slowing the train until the overspeed condition is cleared.
If the Engineer has an MAS (Maximum Authorized Speed - 80 MPH in LIRR EMU cars) code, he can physically do any speed from 0 - 80. If he goes above 80, the brakes will apply. That enforcement applies to any speed limit associated with whatever code is present in the rails. It cannot be exceeded.
The main beauty of the system is it is fail-safe. Track circuit failure, broken rail, etc, will produce the most restrictive code, I.E., no code.
Tom
by RC '75
Hi Tom,
My question is about relays and trainlines. I've been reading in this post and many others about these two items. Is it even possible to answer how many relays and trainlines are involved in a LIRR MU train?
Thanks....
My question is about relays and trainlines. I've been reading in this post and many others about these two items. Is it even possible to answer how many relays and trainlines are involved in a LIRR MU train?
Thanks....
by N340SG
RC '75,
It would be much easier to count trainlines than relays. For trainlines, you'd look at coupler pins. Of course, any trainline has to go through the couplers. As for relays, it would take too much time to try to count. There are even relays on some of the printed circuit cards.
One thing I can tell you is the M-7s have a lot more trainlines than the M-1 or M-3. Many critical trainlines in the M-7s have redundant paths, and many functions have a positive trainline and a negative trainline associated with them.
Tom
It would be much easier to count trainlines than relays. For trainlines, you'd look at coupler pins. Of course, any trainline has to go through the couplers. As for relays, it would take too much time to try to count. There are even relays on some of the printed circuit cards.
One thing I can tell you is the M-7s have a lot more trainlines than the M-1 or M-3. Many critical trainlines in the M-7s have redundant paths, and many functions have a positive trainline and a negative trainline associated with them.
Tom