BR Class 37 Diesel Scheme
The British Rail Class 37 is a diesel-electric locomotive. Also known as the English Electric Type 3, the Class was ordered as part of the British Rail modernization plan.
The Class 37 became a familiar sight on many parts of the British Rail network, in particular forming the main motive power for Inter-City services in East Anglia and within Scotland. They also performed well on secondary and inter-regional services for many years. The Class 37s are known to some railway enthusiasts as "Tractors", a nickname due to the agricultural sound of the diesel engine of the locomotive.
Copright © Digitrax Inc. July 8th 2007
SDF: Class37 "Loch Trieg" Diesel Scheme
Author AJ Ireland
(A) Function Key Usage:
F2- Horn, [CV150 selects Horn type]
F3- Coupler crash [Autocoupler/brake set by CV151 max spd]
F4- Air feature disable- F4 to OFF enables pop-off,drier and starts compressor
F7- Crossing Gate Airhorn - or Manual Notch DOWN, if CV155 is not 00
F8- Mute control, [F8 ON is muted.]
F9- Engine Brake squeal
F10- Crossing gate Airhorn sequence
F11- Sanding cycle
F12- Cab door closing
(B) class37 Sound FX defined CV's: [decoder CV8=8 Factory reset value in sq. brackets]
CV58 Master Volume, 0-15, 0= max, (F8 used for Mute) 
CV122 Product TYpe, 12 = Digitrax SFX sound decoder (Read Only Value)
CV123 Hardware Version (Read Only Value)
CV132 Notch rate 
CV135 Volume when Muted 
User configurable SoundCV's:
CV140 PRIME mover vol 0-64 
CV142 Horn volume 0-64 
CV143 Air features volume (popoff, drier,comp) 0-64 
CV145 Misc vols 0-64 
CV147 Drier rate, 1= about 2secs 1-64 
CV148 Compressor Start rate 
CV149 COMPRESSOR ON time 
CV150 Horn Selector 0=std BR Horn , 1=Playable volume Horn 2=Alternate BR Horn 
CV151 PEAK speed to allow AUTO coupler/brake on DIR change and F3 on. 0-60 
CV152 Author ID Digitrax=0xdd 
CV153 Project ID BR class37 
CV155 Notching Mode,0=AUTO, 1=SEMIAUTO,2=MANUAL NOTCHES 
(C) General Notes
This sound recording courtesy of South Devon Heritage Railway, Buckfastleigh, Devon, UK.
Special thanks to Driver, Andy Matthews, Devon Diesel Society President and Richard Ellis, General Manager.
All sounds recorded by AJ Ireland at Buckfastleigh, Devon, June 2007.
Note: This Class37 prime mover has significant low-frequency components at idle and low throttle settings,
so the speaker enclosures should be as large as possible behind the diaphragm to extend adequate frequency response below
e.g. 300Hz. This will ensure a more "full" sound that does not appear thin or "tinny".
Each engine we have recorded has a distinct 'personality', so a particular locomotive example may sound slightly different
due to unique e.g. tappet, crank-rate shell vibrations and exhaust-stack differences. Horns and bells are often moved between locomotives, and
some roads may change/upgrade prime-movers, or change a normally aspirated engine with turbo-chargers etc.
This 40 year old "Loch Trieg" unit has a 1,750 Hp V12 English Electric Dual Intercooled and Turbocharged diesel engine.
This SDF is approximate for UK. For example, the F7 crossing horn-blow is not the UK practice, and these locos do not have an F2/bell.
UK carriage (car) brakes employ a vacuum, unlike the US practice of the Westinghouse
pressure driven brake cylinders. (UK Brake-stands make "sucking" instead of 'blowing' sounds)
With Digitrax Sound FX decoders and downloadable sound project files (.spj), you can download your choice of sound schemes into any Sound FX equipped locomotive. You can use spj’s that are available for free, you can modify those schemes or you can create your own!
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