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ZS37P Class 37 ActiveDrive SL Enhanced V19.01

Please spend a few moments to read these notes which have been produced so that you may obtain the maximum satisfaction from your new sound scheme.

The sounds should work perfectly when the decoder is fitted correctly. Individual locos may require some fine tuning that you can achieve with your DCC controller.

What is ActiveDrive SL Enhanced?

This is a system developed to allow more prototypical sounds to be deployed across a wide range of operating conditions.

The sounds have been programmed in such a way that you, the user, may change the way that the sounds respond to your driving style or needs. This avoids the need for reprogramming and all the additional costs that would imply.


Engine Start Up.


The fuel lines are pressurised with a priming pump prior to starting. F14 has the sound of this pump which can be played before switching on the main engine sounds.


I have separated this from the start up sounds so that you can choose to use it or not.


F 1 will crank and start the engine which will then settle down into Idle


Multiple Starting Options

The sound is switched on/off and the engine started and stopped with F key 1

After driver checks and switching on the BIS (Battery Isolation Switch) starting a real Class 37 from cold first requires the fuel lines to be pressurised. An electric priming pump is supplied for this.

Your decoder has the Priming Pump sound assigned to F key 14 which will operate prototypically with the engine sounds off. This allows you to choose when to use it and your required duration. (Note: In order to obtain the prototypical sequence of sounds before a Cold Start you should engage F14 for as long as you wish and then disengage immediately before engaging F1).

You can then choose a cold start, which exhibits a longer period of engine cranking before the engine fires, or a warm start where the engine fires immediately.


Engage F key 5 before using F key 1 to start the engine.


Disengage F key 5 before using F key 1 to start the engine.

In both cases, after the engine has started engage or disengage Fkey 5 depending on the driving style you wish to use.

New Feature. Toggling F5 whilst stationary will cause the sound to transition between warm and cold idle sounds.


Throttle Response Scheme.

As supplied, the decoder will produce the sounds of a Class 37 with a train on the hook.

After the start-up routine the loco will stand with the diesel engine, the Prime Mover (PM), ticking over at idle.

The sounds will respond to the throttle control in the following way:

Select speed step 1. The brakes will release, the PM will increase power to get the loco moving, and will continue until at higher speed, a further ramp up will be initiated until the final high speed running sounds begin. The precise speed steps will depend upon your model, so I suggest you make a note of the actual figures for your later use.

The sounds will spool down at similar points on deceleration.

The model can be driven in this way without ever needing to use any control other than the throttle .

For those of you who prefer something more immersive, in this custom version there are extra control features to further enhance your driving pleasure.


No matter what actual speed your model is travelling at, or which engine note range is playing, reducing the throttle by 10 speed steps (of 128) will spool down the engine sounds to ‘Coasting’

The coasting sound will continue until you accelerate; at which point the sounds will change to those relevant to the current speed.

Alternatively, to force the engine to play idling sounds, or to avoid engine ramp up when pottering about the yard, use F6 at any time

Notch Down

During any driving sound ‘loop’, at any speed, it is possible to cause the engine power to spool down to the level immediately below. This is easily achieved by reducing the speed by one step only E.g., if the loco is playing power band 3 sounds, reducing speed with your throttle by one step will cause the sound to immediately spool down to the sound of power band 2, if in power band 1, it will spool down to idle.

Acceleration of one speed step or more will immediately ramp the sound back up to the higher power. So you can now, at any road speed, vary the engine note by reducing or adding a single speed step.

Heavy Train/Light Engine Modes

The default setting is for ‘heavy train’. Inertia is high so acceleration (and deceleration) is restricted.

Activated by F5, Light Engine mode enables multi-function changes with one key. The switched features include reduced inertia setting to allow more rapid acceleration.

F5 can be operated at any speed to give another way in which the engine sounds at a given road speed may be modified instantly.

You can use this feature at any time.

Note. This F key is also used for the alternative, cold,  start so the tick-over sound at Idle will also change to cold idling in which the engine ‘hunts’.

Dynamic Inertia

A combination of new features is included in the automatic operation of the throttle which will affect how the model responds to your control inputs.

The operation is identical in either ‘heavy’ or ‘light’ mode.

Put in simple terms, the wider you open the power controller, the quicker the engine sounds ramp up and for the first time on any decoder, the acceleration rate increases correspondingly.

What does this mean in practice?

If you use your controller’s throttle gently, with modest speed step increases, then the engine will rise and fall automatically and the model will accelerate according to the momentum setting. This is by default high for ‘heavy’ and low for ‘light’.

If however, you open the throttle rapidly, the engine will ramp up to full power and acceleration will be approximately 3 times quicker. This change in acceleration rate is variable and dependent upon throttle operation.


You may have heard real Class 37s the engines of which appear to be either ticking over at idle or thrashing at full chat.

At other times, a more sympathetic driving style will produce steadily rising and falling engine revs.

This sound project is set up to allow you, the operator, to drive in a number of different styles.

Gentle increases in speed steps will produce a linear progression through the power bands, related more to road speed than power settings.

On the other hand, large throttle increases will cause a rapid increase in engine power sounds – so called ‘Binary Driving’ (power is either at minimum or maximum with no shading in-between).

Operating the throttle at any point between these extremes will produce a mixture of the two styles, the exact nature of which will depend on the particular way it is used in each event.

This mirrors closely what happens in real Class 37 locos

To give you a more precise control over the outcomes of your various styles, you can tune the sensitivity of this feature with CV387 to match the effect you wish to achieve. The default value is 50; use lower values to reduce the impact of this feature or for a very rapid increase in power sounds use higher values up to a maximum of 255.

Here’s a simple illustration.

From standing, open the throttle to speed step 30 (of 128). The engine revs will increase moderately then after a short duration the engine power will spool down.

From standing, open the throttle to roughly 80 speed steps and immediately reduce to 30 speed steps. Although the final velocity of the model will be the same as before (30 speed steps) in this case the loco will accelerate with full engine power sounds before spooling down.

Low values in CV387 will facilitate the former whilst high values will make the latter more easily attainable.

Speed Lock

This feature allows the road speed to be locked whilst the throttle control is used to control the engine power sounds playing.


Accurately simulating the sound of a heavy train slowly climbing a gradient with engine at full power is as easy as depicting it coasting down a gradient with the engine at Idle with this single new feature.


Here’s how it works. Engage the SpeedLock Key, (F7) to fix the model’s road speed temporarily. The throttle now directly controls the engine sounds only. Increase speed steps to apply more power, decrease speed steps to spool the engine down to lower power bands or to Idle.


Disengage the SpeedLock Key when you wish to return control of the model’s speed to the throttle.


Engine Speed-up

This differs from Speed Lock in that it can be used whilst the throttle is still in use to control road speed.

F8 is a complementary key to F6. Whilst the latter forces the engine sounds to Idle, F8 will speed up the engine to maximum. Remember to switch this key off before stopping!

Working Loco Brakes


In a real locomotive, acceleration, speed and deceleration are under control of the driver. He will use his experience of the locomotive type, the train weight and knowledge of the route (or ‘Road’) to anticipate the control movements required to achieve the required performance and safety.


Deceleration is often achieved by reducing power only, allowing the locomotive to ‘coast’ to lower speeds. Typically, the brakes are only used to fine tune this rate of deceleration or make a halt at a specific point. Other times, strong braking will be required even at high speed.


A feature notably lacking in all other programmable decoder brands with UK sounds, is the ability to apply a variable braking force to increase the rate of deceleration when desired. This makes stopping a heavy train at a signal or station platform more difficult than it is on a real loco.


Without brake force, the locomotive’s dynamics are only partially modelled. There is no point in having the sound of brakes being applied if the rate of deceleration is unaffected.



The objective is to simulate the real driving experience as closely as possible, so here’s how it works.


For optimum control and convenience, the feature needs to be assigned to a non-latching (or momentary) key. On many non-European designed DCC controllers, the only momentary key is F2. Some, like NCE PowerCab have a designated separate key which operates F key 2 from a dedicated Horn/Whistle button.

The sound project has been constructed to take these limitations into account, so the Horn/Whistle button becomes the Brake Key. (Don’t worry, the horn will not blow when you apply the brakes!).


Reduce the throttle setting to zero. The loco will coast, gradually decelerating and the engine will spool down directly to idle.        


Engage Brakes with F key 2.


A short ‘dab’ will produce a short air release sound and a modest increase in deceleration rate. You can think of this as ‘Speed trimming’. This can be repeated if required, and is entirely prototypical in operation.


A longer application will produce a longer air release sound and a higher rate of deceleration.


The longer the Brake Key is held ‘on’, the greater the brake force applied


Holding the Brake Key down continuously will produce a long air release sound and the loco will perform a prototypically modelled emergency stop, i.e. Brake force increases with time; maximum brake force and deceleration rate is achieved immediately prior to coming to a halt.


Automatic brake squeal will accompany the final moments before halting.


The Brake Key can also be used to simulate ‘brake dump’ testing.


The Brake Key may also be operated during deceleration between different speeds, e.g. speed restricted areas. In this case, reduce the throttle to a suitable lower setting. The engine sound will change according to the features described earlier, so may result in a different power sound rather than engine idle. To increase the rate of deceleration, use the Brake Key as before, and the speed of the loco will be ‘trimmed’ to the newly selected speed step.


So there are no excuses available for a SPAD event.


Please note that real locos do not stop dead even during an emergency stop. To reflect this, an emergency stop will be reasonably abrupt but not sudden.


If your DCC controller is equipped with a ‘panic button’ to avert imminent catastrophe, this will still operate as usual, and will have more immediate, though less prototypical, effect than the Brake Key.


Enhanced Sound Features


I have changed the way in which some sounds work or are triggered in order to enhance the simulation of real railway sounds.


Flange Squeal

Enabled with the F Key 9; if it is not engaged, the Flange sounds will not play under any circumstances.


If the key is engaged, sounds will operate in the following automated way:


Loco is stationary or comes to a halt. The wheels are not turning and so there would be no flange squeal in reality. No flange sound will play in your model.


Loco is moving slowly. A slow speed flange squeal will play.


Loco is moving more quickly. A faster speed flange squeal will play.


Wagons Snatching and Buffering


Enabled with F Key 13; if it not engaged, the wagon Snatching and Buffering sounds will not play under any circumstances.


If the key is engaged, and the Light Engine Mode (F key 5) is also engaged, the sounds will not play under any circumstances. (No wagons coupled in Light Engine Mode).


If the key is engaged, and the Light Engine Mode (F key 5) is not engaged, sounds will operate in the following automated way:


Loco is stationary. The sounds are not played.

Loco moves off/accelerates gently. The sounds are not played.

Loco moves off/accelerates more rapidly. The sound of the couplings taking up slack as the train stretches plays. This is also the case if the loco accelerates further when already moving.

Loco decelerates gently. The sounds are not played.

Loco decelerates more rapidly. The sound of several wagons buffering up is played each time.

Loco comes to a halt with the Brake Key (F key 2) engaged. The sound of several wagons buffering up is played after it comes to a halt.



New to this version, there are 12 different Horn sounds which are selected automatically by the decoder depending on speed and direction.

These have been included to more closely follow typical practice – short ‘toots’ to warn of intended loco movement and long blasts when travelling at high speed.

These are still controlled by F key 3 and F key 4 but a short ‘Acknowledgement’ version of each will play when the model is stationary. A different sound will play if the model’s intended direction is changed.

 When the loco is moving at speed steps between 1 and 50 different and longer sounds will be played.

When travelling at over 50 speed steps long duration sounds are played.

Live Volume Control

Provided the sound is switched on and the ‘fade’ button is not active, it is possible to change the overall  volume to suit changing needs.

Engage F27 and the sound levels will gradually reduce, eventually to silence

Engage F28 and the sound levels will gradually increase, eventually to maximum.

In each case, disengage the F key when the desired level is attained. Set F27 and F28 as ‘momentary’ if your DCC controller allows you to do so.

Note: If the volume controls appear to not function, check that F19, F27 and F28 are disengaged before making a further attempt.

Shunt Mode  For precise control when shunting, engage Shunt Mode with F21. This reduces speed by one half whilst inertia and momentum are removed completely. It’s now down to your skill and knowledge to simulate any eventuality!

Function List


F Key



Setting CV





Sound On/Off



Brake Key (see text)



Low Toot Horn (Direction dependent and Speed Related)



Two Tone Horn (Direction dependent and Speed Related)



Cold Start/Light Engine



Engine Idle/Coast



Speed Lock



Engine Speed-up



Enable Speed Related Flange Squeal



Cab Lights (Function Outputs 1 and 2)



High Toot



Spirax Valves



Enable Automatic Wagons Buffering












Dispatch Whistle



Door Slam



Fade All Sounds



Rear Lights (Function Outputs 3 and 4)



Shunt Mode


















Volume Down



Volume Up








Your decoder is configured for white lights on F key 0, tail lights on F key 20 (only if physically separated from the whites), and cab light(s) on F key 10


If your model includes or if you intend to add lighting then in order for the decoder to operate individual or pairs of lights, they must have physically separate connection to the decoder as follows.


No 1 End          white lights to Function Output 0f (white wire in the case of wired decoders)
                        tail light to Function Output 3 (green wire in the case of wired decoders)

                        cab lights to Function Output 1


No 2 End          white lights to Function Output 0r (yellow wire in the case of wired decoders)
                        tail light to Function Output 4 (brown wire in the case of wired decoders)

                        cab lights to Function Output 2



All lighting features soft ‘on’ and ‘off’ by default. This is to simulate the way that tungsten lamps warm up and cool down. Additionally, lamps have been dimmed to be closer to realistic illumination levels. (To make them brighter if you wish, increase the value in CV60).



Paul Chetter


January 2019


Delivery & Returns

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