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Old level crossing yodalarm tone frquencies?

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Old level crossing yodalarm tone frquencies?

Unread postby levelcrossingguy » Mon Apr 13, 2015 11:15 pm

Hi,

Is anyone aware of the frequencies for the yodalarms that were installed at older crossings? I know the most recent frequencies are 800Hz - 1000HZ at a rep of 500ms (0.5s).

The tone I am looking for is like this one installed at this level crossing: https://www.youtube.com/watch?v=EFxFZs9jMEM

It would be greatly appreciated if anyone could help me as I just keep hitting dead-ends on trying to find the frequencies.

Thank you,

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Re: Old level crossing yodalarm tone frquencies?

Unread postby John Webb » Tue Apr 14, 2015 8:57 am

As far as I am aware, 'Yodalarms' came with several different frequencies and repetition rates selectable by switches or jumper wires - at least those used in fire alarm systems did when I was involved in such things. So reference to a data-sheet may be of help? (But of course BR may have insisted on fixed frequencies to ensure things were not accidently altered!) Alternatively load the sounds into a program such as 'Audacity' where you can closely inspect the waveform against a time-base and get an estimate of the frequencies/duration that way.
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Re: Old level crossing yodalarm tone frquencies?

Unread postby scarpa » Wed Apr 15, 2015 10:08 am

I have come across several newer level crossing installations where if another train on adjacent line was approaching before the crossing controls normalised the yodalarms would change their tone.One crossing I remember was an Open type in West London
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Re: Old level crossing yodalarm tone frquencies?

Unread postby Mike Hodgson » Wed Apr 15, 2015 11:03 am

Yes, you only get the double speed yodel on double track lines at AHBs/ABCLs/AOCLs; it's not necessary with full barriers or single lines. There is a newer type called Apello which gives a spoken message instead : http://www.e2s.com/case-studies/network ... n-sounders

The OP asked about the early crossings. I thought the very earliest ones had bells, or was that just the MCBs? I suspect the type of audible alarm may sometimes be specified in the level crossing order.

GK/RT0300 (Issue One, dated August 1998) specifies :
5.1
When the level crossing operating cycle is initiated, the Audible Warning Unit
shall emit a sound comprising two alternating repeating signals.
5.2
The emitted sound shall alternate at an increased rate where a second (or
subsequent) train approaches during the level crossing operating cycle.
5.3
The sound pattern shall be sufficiently distinct from other systems in the area
of the level crossing (e.g. Pelican, Puffin Road Crossings and TOWS) as to not
cause any potential confusion amongst pedestrians and other road users.
5.4
The nominal audible signal output shall be capable of adjustment in volume to
suit local background noise conditions including selection for differing
requirements of day and night conditions. The adjustment shall be achieved
from a source external to the Audible Warning Unit.
5.5
Permitted variations in the specified power supply shall not lead to obvious
variation of audible characteristics. This shall including any loading effects on
the power supply generated during the Level Crossing operating cycle.

6.1
The two alternating signals shall have frequencies of 800Hz ±1% and 1000Hz
±1% and equal duration.
6.2
The tonal sequence required in 5.1 shall repeat every 0.5s.
6.3
The tonal sequence required in 5.2 shall repeat every 0.25s.
6.4
The audible signal output shall be adjustable to give outputs ranging between
80dB(A) and 60dB(A), measured at a distance of 3m radius from the unit,
taking into account the effects of phase cancellation between units.
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Re: Old level crossing yodalarm tone frquencies?

Unread postby StevieG » Thu Apr 16, 2015 12:55 pm

Mike Hodgson wrote: " .... I thought the very earliest ones had bells, or was that just the MCBs? .... "
In the mid-late '70s I did a mini-tour of a few crossings near us that had then been recently re-equipped, with, or in preparation for, general resignalling.
Litlington AHB I'm sure had loud trembler bells, sounding when the crossing was activated, until the barriers were down ( & of course, it also then had the 'neon'-type ATC signs for 'second train').
Everton (then controlled by the adjacent new GB), and Tempsford (CCTV, by Everton GB) were both MCBs : One of them had a slightly pathetic sounding small bell 'ting'-ing on each road approach to the crossing while the lower sequence was operating, each sounding approx. once per second but apparently synchronised so that they sounded alternately, giving a total 'ting' rate of about twice per second: The other crossing had yodalarms : As I seem to recall thinking that maybe Yodalarms had been introduced for the (then still uncommon) remote CCTV-supervised crossings, I think that they were at Tempsford, and the 'ting ting's were at Everton.

On Yodalarm tones, unfortunately I can't relate the Hz figures to what the alarm units sound like, but I believe that, in those that I came across, the audible difference between the tones was once similar to that between the two tones once used on most emergency-service vehicles, but that I think I have since heard instances where, although the high tone has still been much the same, the low tone in some has been a semi-tone nearer to the high, and some where it has been a full tone nearer to the high (resulting in possibly being only one full tone below the high).

[ Edited 00:45 17/04/15, to correct strange spelling error.]
Last edited by StevieG on Thu Apr 16, 2015 11:45 pm, edited 1 time in total.
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Re: Old level crossing yodalarm tone frquencies?

Unread postby scarpa » Thu Apr 16, 2015 1:12 pm

The A H B s installed pre Hixon were initially equipped with loud Bells .Some remained until the 1980 s. Mile End Crossing East Anglia was one
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Re: Old level crossing yodalarm tone frquencies?

Unread postby davidwoodcock » Thu Apr 16, 2015 2:54 pm

I visited Barnes box in April 1963 which controlled a pair of full-barrier-equipped level crossings which were nearly adjacent in road, but not rail, terms (being on diverging rail routes). Both crossings were equipped with loud bells. On the same day, I also visited Hampton Court box which had a wheel-worked gate-equipped level crossing which had neither lights nor bells (I was told not to look at the crossing as I worked the wheel to close the gates - "there is nothing like a few good dents to persuade the b*gg*rs not to try it on".)

I would say that this was just after (by a year or so) the general change from bells to two-tone sirens (and blue flashing lights) on emergency vehicles.
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Re: Old level crossing yodalarm tone frquencies?

Unread postby Mike Hodgson » Thu Apr 16, 2015 4:46 pm

StevieG wrote:Litlington AHB I'm sure had loud trembler bells, sounding when the crossing was activated, until the berries were down ( & of course, it also then had the 'neon'-type ATC signs for 'second train').


It finally had its wig wags replaced after the new ones spent a few months lying on the ground to their adjacent to their bases earlier this year, but the ATC lights had already gone a couple of years ago, probably one of the last places with them? I presume the yodals would have been renewed along with the lights.
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Re: Old level crossing yodalarm tone frquencies?

Unread postby Tom O'Flaherty » Wed Jul 1, 2015 10:24 pm

It sounds to me like it's alternating between 800 and 880Hz.

There are some notable harmonics in the mix there but I have not had the chance to carry out any actual spectral analysis.
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Re: Old level crossing yodalarm tone frquencies?

Unread postby Fast Line Floyd » Thu Jul 2, 2015 9:39 am

davidwoodcock wrote:I visited Barnes box in April 1963 which controlled a pair of full-barrier-equipped level crossings which were nearly adjacent in road, but not rail, terms (being on diverging rail routes). Both crossings were equipped with loud bells. On the same day, I also visited Hampton Court box which had a wheel-worked gate-equipped level crossing which had neither lights nor bells (I was told not to look at the crossing as I worked the wheel to close the gates - "there is nothing like a few good dents to persuade the b*gg*rs not to try it on".)

I would say that this was just after (by a year or so) the general change from bells to two-tone sirens (and blue flashing lights) on emergency vehicles.

Barnes Box in 1963 had one set of Hydro pneumatic operated gates local to the box and no bells, the other crossing in Vine Road was controlled locally by a Gate Box called Barnes Windsor Line Crossing which had wheel worked gates and no bells.

The crossings were converted to full barrier crossings in 1973 along with the rest of the crossings on the Windsor Line as part of the Feltham resignalling scheme (although Barnes box remained and took control of all of the crossings), at this time the full barrier crossings on the Southern all had bells.
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Re: Old level crossing yodalarm tone frquencies?

Unread postby davidwoodcock » Thu Jul 2, 2015 10:13 am

Fast Line Floyd wrote:Barnes Box in 1963 had one set of Hydro pneumatic operated gates local to the box and no bells, the other crossing in Vine Road was controlled locally by a Gate Box called Barnes Windsor Line Crossing which had wheel worked gates and no bells.



That had been the historical situation at Barnes, but the reason we were specifically taken to the box in April 1963 was to see the new installation with both crossings controlled from separate pedestals (each situated in the nearest corner of the operating floor to its crossing) within the same box. The fact that barriers with bells and lights had been installed was considered an important factor because the stretch of road between the two crossings was very short - it enabled both crossings to be closed when necessary to prevent rush-hour tail backs blocking one or other crossing, no yellow boxes in those days even though obstructing a crossing was a statutory offence (obstructing a railway signalman in his duty).
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Re: Old level crossing yodalarm tone frquencies?

Unread postby Fast Line Floyd » Thu Jul 2, 2015 12:51 pm

davidwoodcock wrote:
Fast Line Floyd wrote:Barnes Box in 1963 had one set of Hydro pneumatic operated gates local to the box and no bells, the other crossing in Vine Road was controlled locally by a Gate Box called Barnes Windsor Line Crossing which had wheel worked gates and no bells.



That had been the historical situation at Barnes, but the reason we were specifically taken to the box in April 1963 was to see the new installation with both crossings controlled from separate pedestals (each situated in the nearest corner of the operating floor to its crossing) within the same box. The fact that barriers with bells and lights had been installed was considered an important factor because the stretch of road between the two crossings was very short - it enabled both crossings to be closed when necessary to prevent rush-hour tail backs blocking one or other crossing, no yellow boxes in those days even though obstructing a crossing was a statutory offence (obstructing a railway signalman in his duty).

Yes but not 1963 definitely 1973 or there abouts, the work was only done as part of the Feltham resignalling. I didn't get to visit Windsor Line Crossing box until 1968 and Barnes panel the following year, I have a photograph taken in 1973 from Barnes Panel looking at the old gates and the new barriers about a week before changeover. For it to have been 1963 I would have been 8 years old and I know I wasn't....
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Re: Old level crossing yodalarm tone frquencies?

Unread postby davidwoodcock » Thu Jul 2, 2015 2:08 pm

Sorry but it was definitely unquestionably 1963. I was still at school and on a one week "introduction to Southern Region S&T" Easter holiday residential course (and what an introduction, I might add, for someone who had already devoured borrowed copies of all the IRSE green books). We were taken there specifically to see the new installation, having visited an "old style" level crossing box at Hampton Court earlier that day.

We were allowed to operate the buttons that raised and lowered the barriers, watching the "other crossing" on the TV monitor - although it could be seen clearly with the naked eye.
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Re: Old level crossing yodalarm tone frquencies?

Unread postby Fast Line Floyd » Thu Jul 2, 2015 2:17 pm

davidwoodcock wrote:Sorry but it was definitely unquestionably 1963. I was still at school and on a one week "introduction to Southern Region S&T" Easter holiday residential course (and what an introduction, I might add, for someone who had already devoured borrowed copies of all the IRSE green books). We were taken there specifically to see the new installation, having visited an "old style" level crossing box at Hampton Court earlier that day.

We were allowed to operate the buttons that raised and lowered the barriers, watching the "other crossing" on the TV monitor - although it could be seen clearly with the naked eye.

That sorts it out as CCTV crossings didn't exist anywhere until 1971 following a trial in 1970 and certainly not at Barnes. Oh and my Mother would never have let me out on my bike to visit signalboxes on my own at the age of eight - I lived around 6 miles from Barnes at the time. PM me with your email address and I'll send you the photo.
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