Semi-automatic Signals

[louis97]

Whats the difference between a Automatic Signal and a Semi-Automatic Signal?

I know what a Automatic Signal is, but am baffled by the Semi Automatic, because surely its either the signaller controls it, or the signaller dosent?

Thanks in advanced

 

[Daniel]

Most simply a semi-automatic it is automatic because it automatically returns to red once a train passes it, but semi because a signaller changes it to green.

A fully automatic signaller returns to green itself once the appropriate block sections are clear =)

 

[louis97]

Most simply it is automatic because it automatically returns to red once a train passes it, but semi because a signaller changes it to green. =)

But wouldent that make that signal a controlled signal as its the signaller who puts it back to green?

 

[Old Timer]

Whats the difference between a Automatic Signal and a Semi-Automatic Signal?

I know what a Automatic Signal is, but am baffled by the Semi Automatic, because surely its either the signaller controls it, or the signaller dosent?

Thanks in advanced

Simple explanation.
A semi-automatic signal IS controlled by the signalman but is set up to work as an automatic in the normal course of events.

Semi-autos generally protect emergency crossovers, and level crossings, but can protect other situations.

The difference on the panel is that a semi-automatic does not have a route setting ability, simply being controlled from auto to red by means of a switch or button which acts as the release for other equipment.

In the case of a crossover, the track circuits have either to be clear or specific track circuits have to be occupied for a prescribed period before the release will release the local lever frame or control panel.

In the case of a level crossing controlled by a level crossing keeper, the signal is controlled from the level crossing by means of the crossing keepers panel. No route setting is involved, the LC keeper simply presses the crossing clear button and then releases the control on the signal protecting the crossing, which will go to automatic mode.

 

[GB]

An automatic signal is where the signal is controlled purely by the train operating the track circuits and has *no control from the signaller.

A Semi Automatic signal has the ability to either work as an automatic signal (ie the signaller can leave the switch controlling the signal "off" and there by allowing the signal to be controlled by trains operating track circuits like an auto signal) or he can physically control the signal for each train.

Im sure someone can offer a more technical explanation.

*not including any emergency replacement features if applicable

 

[louis97]

Simple explanation.
A semi-automatic signal IS controlled by the signalman but is set up to work as an automatic in the normal course of events.

Semi-autos generally protect emergency crossovers, and level crossings, but can protect other situations.

The difference on the panel is that a semi-automatic does not have a route setting ability, simply being controlled from auto to red by means of a switch or button which acts as the release for other equipment.

In the case of a crossover, the track circuits have either to be clear or specific track circuits have to be occupied for a prescribed period before the release will release the local lever frame or control panel.

In the case of a level crossing controlled by a level crossing keeper, the signal is controlled from the level crossing by means of the crossing keepers panel. No route setting is involved, the LC keeper simply presses the crossing clear button and then releases the control on the signal protecting the crossing, which will go to automatic mode.

Thanks very much for the explanation

How would you go about if a crossover was controled by the signaller? but there was no signal for him to signal the train to on the other line

 

[GB]

Thanks very much for the explanation

How would you go about if a crossover was controled by the signaller? but there was no signal for him to signal the train to on the other line

If there is no signal to allow the train onto the other line then it would be an unsignalled move and would only be done under certain circumstances not under normal day to day operations.

 

[louis97]

If there is no signal to allow the train onto the other line then it would be an unsignalled move and would only be done under certain circumstances not under normal day to day operations.

So for single line working due to engineering works with a pilotmen?

 

[Old Timer]

The ground frame operator will operate the points and the Pilotman will authorise the train to proceed through the crossover in the relevant position

 

[Muttley]

Not wanting to complicate things, but...

...you won`t know (from a non-S&T point of view) whether the signal is an auto, semi-auto or controlled signal. And from an everyday point of view its irrelevent. I suspect you`ve seen a sign on the signal post. All this tells the driver is how to act if stopped by a red and theres no communication with the signaller.
ie any type of signal may have any/no sign on it, depending upon the desired reaction wanted.

 

[Metroland]

Unless I've misunderstood the above post:

Semi automatic signals have a white line on the plate and the word semi. Automatics just have the horizontal white line. Controlled are usually black (white in some areas) and painted with the signalbox name:

EG

W12 Wimbledon 12 signal
PN22 Preston 22 signal
CE12 Crewe 12 signal

and so on

Intermediate block signals have a vertical white line on, and exist in absolute block areas where you have remote (usually) colour lights.

Drivers can pass automatic signals and IBS signals, and semi autos (if the controlling box/Ground frame is closed) if there is no communication and they have been halted at the signal. The driver should stop at the next signal if its showing proceed.

On older installations usually 1 out of 5 signals can be replaced to danger on an auto section and are not guaranteed to return to danger. On newer ones every signal can be replaced and they are guaranteed. Auto signal indications are not normally shown to the signaller, except in some IECCs.

 

[GB]

Not wanting to complicate things, but...

...you won`t know (from a non-S&T point of view) whether the signal is an auto, semi-auto or controlled signal. And from an everyday point of view its irrelevent. I suspect you`ve seen a sign on the signal post. All this tells the driver is how to act if stopped by a red and theres no communication with the signaller.
ie any type of signal may have any/no sign on it, depending upon the desired reaction wanted.

Then surely by that virtue you can tell the difference by the way its plated otherwise how would the driver know how to act if he came to a red signal with no comms as drivers cant pass controlled signals under their own authority.
--- old post above --- --- new post below ---

Semi automatic signals have a white line on the plate and the word semi

Yes, here is an example...

http://www.east-rail.fotopic.net/p55592159.html

 

[Muttley]

Then surely by that virtue you can tell the difference by the way its plated otherwise how would the driver know how to act if he came to a red signal with no comms as drivers cant pass controlled signals under their own authority.

You mis-understand me.
The plate tells how to act (when at red). It does not say who/what works it.

The actual nuts and bolts of how the signal works is completely irrelevent. It makes no odds what so ever if theres a signaller, a track circuit, or fairy magic. All over the system there are autos plated as controlled, controlled plated as semis, and every other possible variation.