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Logic of circuit letter Nomenclature

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Logic of circuit letter Nomenclature

Unread postby panelbeater2 » Fri Jun 7, 2013 7:20 pm

Can anyone explain the "logic" behind the circuit letter nomenclature?

I give as examples:-

G = Signal
H = Caution [yellow]
K = Indicating or detecting
W = Points

and many more......

Many thanks

Neil
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Re: Logic of circuit letter Nomenclature

Unread postby JRB » Fri Jun 7, 2013 7:48 pm

This was discussed way back, but in spme cases the obvious choice already meant something else. W looks like points in plan and also stands for Weichen (Points in German). The relays controlling signal motors or lights are simply HR for Home off (or yellow) and DR for Distant off (or green). If you spend a few days looking back through the archive, you'll find the rest.
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Re: Logic of circuit letter Nomenclature

Unread postby baconandeggs » Fri Jun 7, 2013 9:20 pm

panelbeater2 wrote:Can anyone explain the "logic" behind the circuit letter nomenclature?

I give as examples:-

G = Signal
H = Caution [yellow]
K = Indicating or detecting
W = Points

and many more......

Many thanks

Neil


The apparatus naming conventions used in New Zealand are explained here

http://valleysignals.org.nz/petone/apparatusnames.html

NZ followed both UK and North American practice. The original automatic signalling installations in the 1920s were based on US practice so maybe the naming conventions are similar to those used in North America, but I do not know. Maybe someone else can comment :D

I think that your question is about the reason for choosing particular letters for each item of hardware. My guess is that someone had a piece of paper with the letters of the alphabet written on it and assigned them almost at random as required, but I do not know. This is similar to the intense discussions among loco enthusiasts who are determined to find a rational reason why a particular loco class was, for example, called DL rather than DK because "K" is the next available letter in the alphabet (a real example)!
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Re: Logic of circuit letter Nomenclature

Unread postby JRB » Sat Jun 8, 2013 5:43 am

That NZ list is amost exactly B.S. 376 Part 2 as used in the UK.
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Re: Logic of circuit letter Nomenclature

Unread postby MRFS » Sat Jun 8, 2013 10:30 am

W is easy - sWitch.

The majority of codes come from a phonetic or functional hint - roUte Electric indicator Checking Relay - I'm not sure about H - but I came across some clues in an Interboro' document I saw a while back which made me think it came from being half-way between Red and Green. Which also makes sense if you consider Flux Neutraliser signals.

D for green I think comes not from the shape of the circuit itself, but the other use of 'Decoding' or more likely 'Down' because that'd be the way the blade would go for the motor semaphores.
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Re: Logic of circuit letter Nomenclature

Unread postby Bob Davies » Sat Jun 8, 2013 10:43 am

I am sure JRB has it right when he talks about H standing for Home (controls the transition from red to yellow) and D standing for Distant (controls the transition from Yellow to Green). If you look at the nomenclature of relays as used by the Southern Railway, very early wide-spread users of colour-light signalling, you see the complete picture and they did exactly this (although their use of I for Inner (Y -> YY) and O for Outer (YY -> G) was not perpetuated in BS376).

The old Brighton Power Frame installation was a microcosm of this, including the use of PDR for Point Detection Relay!
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Re: Logic of circuit letter Nomenclature

Unread postby baconandeggs » Sat Jun 8, 2013 9:29 pm

JRB wrote:That NZ list is amost exactly B.S. 376 Part 2 as used in the UK.



Thanks for that. I will add a reference to the standard on the web page. I note that in the UK this BS has been replaced with GK/RT0205. I have a a Post Office background and find it interesting that the term "slate" is still used.

To me the important thing is knowing, for example, that "H" means caution or yellow - it is not obvious. Why this letter was used is less of a concern to me.

The naming conventions in BS 376 part 2 are logical. I have not seen many circuit diagrams but I have found that it is (relatively) easy to understand a circuit because the function of a contact is immediately obvious from the designation. It is a very long time since I saw a print (GBW???) of a strowger final selector and I cannot remember if there was a similar logic to the relay designation. I suspect not but could be wrong :D
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Re: Logic of circuit letter Nomenclature

Unread postby JRB » Sat Jun 8, 2013 9:46 pm

Strowger relays certainly followed a strict convention. Where it was laid down I know not, but our telecomms geeks should know. STC train describers largely used telecomms parts & nomenclature. The only relay name which comes instantly to mind is 'PFG' which was defined as a Power Fail Guard relay. The relationship between the name and the function was not obvious (except perhaps to the telecomms types).
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Re: Logic of circuit letter Nomenclature

Unread postby Shunter » Sun Jun 9, 2013 9:27 am

On page 310 of Railway Signalling and Communications, there is confimation of the meaning of D and H stating that they were derived orginally from "distant" and "home".
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Re: Logic of circuit letter Nomenclature

Unread postby DFS » Mon Jun 10, 2013 10:49 pm

JRB wrote:Strowger relays certainly followed a strict convention....

However, according to several apocryphal stories from colleagues, it didn't stop some developers "signing" their work by contriving to design relay sets in such a way that they included relays designated by their own initials. Of course those working in the signalling drawing offices would never dream of doing such things.........
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Re: Logic of circuit letter Nomenclature

Unread postby tjc » Tue Jul 9, 2013 9:02 am

Who would have thought it! As it happens I deliberately avoided introducing a TJCR, and went for a TCZR instead.
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Re: Logic of circuit letter Nomenclature

Unread postby Chris Rideout » Thu Jul 11, 2013 10:59 am

tjc wrote:Who would have thought it! As it happens I deliberately avoided introducing a TJCR, and went for a TCZR instead.

A "special" relay, by the look of it. Wait one, shouldn't your TCZR be a ZTCR?

Also, when the Z is not used as an indication of a special function, there is another way of describing a function. The use of brackets describing certain relays for shunting moves on Standard Tokenless Block as follows:

(SN)NR = Shunt Switch Normal Relay.

(SN)RR = Shunt Switch Reversed Relay.

(SN)SR = Shunt Stick Relay.

(SNCO)R = Shunt Cleared Out Relay.

(O)N = Offer Button (between Botley and Fareham. Originally described as a ZN on the Wilton - Pinhoe section of the former LSWR line).

(TA)N = Train Arrived Button.

Almost everything was different between Botley and Fareham apart from the appearance of the TB instruments. One thing that never changed was the sensitive nature of the apparatus in a thunderstorm. Track circuits would "flashover" when struck by lightning and the block indicators would drop to "Train in section" (unless they were already in that position). If there wasn't a train actually in the section at that time, you could not normalise the block. Ball point pen and failure form in triplicate.
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Re: Logic of circuit letter Nomenclature

Unread postby MRFS » Thu Jul 11, 2013 11:23 am

Bear in mind that tjc does not work for NR so the conventions will be slightly different.

I know that I occasionally have to do a double take when looking at circuits that are ostensibly similar.
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Re: Logic of circuit letter Nomenclature

Unread postby JRB » Thu Jul 11, 2013 10:38 pm

baconandeggs wrote: I note that in the UK this BS has been replaced with GK/RT0205.

Not quite true. BS 376 Pt.2 is till the valid British Standard. GK/RT0205 is only a Network Rail thing. I don't know which Londion Underground, DLR and each of the smaller railways use. They can choose.
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Re: Logic of circuit letter Nomenclature

Unread postby tjc » Fri Jul 12, 2013 2:51 pm

Chris Rideout wrote:
tjc wrote:Who would have thought it! As it happens I deliberately avoided introducing a TJCR, and went for a TCZR instead.

A "special" relay, by the look of it. Wait one, shouldn't your TCZR be a ZTCR?


Maybe, but it's commissioned now! :) I've generally not found Z at the beginning of a name, usually in the middle (e.g. GZSR). I can think of the ZR (Special Computer Control Relay) at Baker Street though (now since decommissioned).

The TCZR in this case was a slow to pick QSPA1 relay energised by the occupation of a track circuit, rather than a straight-forward back contact of a TR as we needed something to 'buffer' the input into a Micronome Timer, which had been repeatedly failing due to track circuits bobbing and contact bounce. I decided against TJCR as it sounded (to me) more like a relay checking the operation of a TJR.
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