Short whistle might make sense in that if you are working in a long tunnel and someone really hangs of the whistle, the sound will echo up and then back down the tunnel again - making it impossible to work out from which direction the engine is approaching (and so which track is the safe one to be stood on - pre H & S of course). A short whistle would help prevent this. Also, if you were faced with two train entering the tunnel from different ends (again assuming twin tracks in same tunnel), if one sounded it's whistle for a long period of time, it could obscure the sound of a train at the other end of the tunnel sounding it's whistle. I guess there may not be one standard anyhow, even amoungst the pe or post grouping railway companies in the UK, let alone compared to the US for example. There is also the plain W convention for whistle, which would imply that if part of the same system, SW would be unlikely to be sound whistle, it would more likely be short. Yours, Rich. On Sat, 12 Jan 2008, Ron Head wrote: > Hi John > > My understanding has always been that it stands for 'Sound Whistle'. > > Regards > Ron > > ----- Original Message ----- > From: "John Pagett" <john_pagett@xxxxxxxxxxxxxxxx> > To: <modeleng@xxxxxxxxxxxxx> > Sent: Saturday, January 12, 2008 9:08 PM > Subject: [modeleng] SW board > > >> I always thought that the "SW" board on the approach to tunnels etc was for >> "Sound Whistle", but I read something the other day suggesting it was >> "Short >> Whistle". > > MODEL ENGINEERING DISCUSSION LIST. > > To UNSUBSCRIBE from this list, send a blank email to, > modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject > line. > MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.