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Summary of CVs - CT Revision 4 Family Decoders

YouChoos Resouces

What is a CV?

The CVs of a DCC decoder are essentially a collection of parameters/variables which influence how the decoder behaves. Many CVs are standard, in that they follow the guidelines set out by the NMRA organisation. However, any fairly advanced decoder will have in addition to this a whole bunch of CVs specific to itself. This is especially true for sound decoders, which provide far more functionality than was ever designed for when NMRA came up with the original standard.

CT's Revision 4 family decoders are no exception, having over 180 CVs for various purposes, some of which I'll discuss in this document. Note that all CT Revision 4 decoders (from Version 40 onwards) share the same CV meanings, although of course some of the CVs are simply ignored on certain decoders where physical features are not available, such as less Function Outputs.

Please note that I have by no means experimented with every CV available, so this is really just a commentary on those areas that I understand. There is yet more functionality that I've gone nowhere near yet - in particular features to support Zimo's Signal Controlled Speed protocol. These look very interesting, but are way beyond where most people will expect to take the decoder.

For the most part, I will be discussing sound configuration, lighting, extended function mapping and motor control. There are of course many 'standard' features within the decoder, which are all NMRA-compliant, such as speed-steps, addressing, basic function mapping etc, and for those I will only pay brief lip-service because they are generally well understand and well documented elsewhere - such as on NMRA's own web site.

Addressing CVs

Let's start with some CVs that are NRMA-standard across the board, relating to loco addressing...

CV(s) Purpose Range (Default) Comments
1 Short address 1-127 (3) For short addresses when CV29 Bit 5 is set at 0.
17+18 Extended address 128-10240 (0) CV29 bit 5 must be set in order to use a long address. CVs 17+18 are used to specify the long address. Please refer to NMRA standards for how this value is calculated.
19 Multi-Unit (Consist) address 0-127 (0) 0 means not in a consist

General CVs

Now let's discuss some of the general-purpose CVs, and those which don't really have a specific category to fit into...

CV(s) Purpose Range (Default) Comments
7 Version Number Read-only specifies the CT software (firmware) version loaded onto the decoder.
8 Manufacturer ID 117 CT Elektronik is always 117. Read-only.
30 Error diagnosis 0-3 1=motor; 2=light; 3=both short-circuit
53 Decoder LOCK/UNLOCK and Access to CVs above 99 on limited systems. 0-255 (0)

Special CV for programming beyond CV99 on old system PLUS decoder LOCK/UNLOCK feature.

For Roco Lokmaus users and any other systems which can only address CVs up to 99. Set bits 0 or 1 to address CVs over 99. Not necessary on most DCC systems.

CV53=66: programming and feedback off (LOCK decoder from accidental re-programming.set to 77 to UNLOCK)

CV53=77: programming and feedback on (UNLOCK decoder for programming. after setting to 66 previously)

CV53=0: 0-99 programmed CV value i.e. CV actually programmed is the one requested

CV53=1: 100+ programmed CV value i.e. with CV53=1, any other CV programming goes to the CV+100, so CV8 would actually be sent to CV108 etc.

CV53=2: 200+ programmed CV value

105 User CV1 0-255 Free for remembering purchase date or similar user information
106 User CV2 0-255 Free for remembering purchase date or similar user information
109 Selection of CV set: 0-1 (0) 0 uses 1st CV set; 1 uses 2nd CV set. Can be used for various purposes - CV set for home layout + CV set for club layout for example. Hard reset will only affect the currently selected CV set. CV109 will be unchanged by a hard reset.
111 Intensity of acknowledgement pulse (ACK) 0-255 (255) Can improve the programming capability, 128 is approx 50% of max acknowledgement pulse (motor dependent) 200 = normal.
137 Special CV 0-255 (0)

Bit 0 (1) - OFF = 8 functions, ON = 14 functions (MAN-bit) refers to F0-F12, btw CV33-CV46 free assignment.

Bit 1 (2) - ZIMO train number impulse on / off

Bit 2 (4) - strong / normal / weak switched with F1, effective only when CV110 is active, and dimmable via CV54

Bit 3 (8) - strong / normal / weak switched with F2, effective only when CV110 is active, and dimmable via CV54CV137

Bit 4 (16) - ZIMO speed contrl - dependent train control 0 = off 1 = on

Bit 5 (32) - Start sequence (Sound Slots 21-23) is played before motor starts to spin - useful for diesel engines in particular as a rev-up sound before phsyically setting off. Beware of using this feature though, as it actually stops the 'standstill' background noise whilst the start-up sound is being played, which can sound a bit odd unless you mix/blend the standstill sound into the start-up sound!

Bit 6 (64) - Set ON if you want to control additional functions using F4 - press twice for F5, 3x for F6, 4x for F7 (useful if your controller does not have access to many functions directly)

Bit 7 (128) - 32kHz frequency motor control from software version 41, factory Bit7 = 0 16kHz

CVs Related to Motor Control

CVs can be used to greatly affect the motion of a loco, and the way the motor reponds to requests. Even an old motor can often be tuned by CVs to make it run smoother than you might expect. Below are presented a few of the SL51-4's motor-related CVs and some comments on how I have used them...

CV(s) Purpose Range (Default) Comments
2 Starting voltage 0-255 Voltage to motor at speed step 1. Tune this if your motor requires a little more umph to get it going, or you may find that the start-off sounds are not totally synchronised with the actual physical moving off of the loco.
3 Rate of acceleration 0-255 Adjust to affect the inertia effect of speeding up. Set to 0 if you want no inertia effect - you control the speed immediately with your controller instead.
4 Rate of deceleration 0-255 Similar to the above CV3, but for realistic slowing down
5 Maximum speed 0-255 0 for no artificial limit (maximum 255 has same effect as 0)
6 Middle speed 0-255 Together with CV2 and CV5 a three-point speed curve can be set. Set CV6 = 0 to give a linear speed curve.
9 Motor PWM 0-255 (134) 13-63 stepless from 30-150Hz,141-191 16kHz for coreless and bell anchor motors
29 Miscellaneous configuration bits 0-255 (2)

Bit 0 (1) - Direction: OFF=normal; ON=inverted

Bit 1 (2) - Speed steps: OFF=14/27; ON=28/128

Bit 2 (4) - Operating mode: OFF=digital only; ON=DC and Digital

Bit 3 (8) - not used

Bit 4 (16) - Speed curve: OFF=default speed curve using CVs 2, 5 & 6; ON=free speed curve using CVs 67-94.

Bit 5 (32) - Address selection: OFF=1-127 (uses CV1); ON=128-10240 (uses CV17+18)

Bit 6 (64) - not used

Bit 7 (128) - not used

50 EMF intensity: 0-255 (255) How strong is EMF effect: 0=no influence; 255=maximum. If you plan to use locomotives in a consist then use a lower value. This reduces the effect of locos working against each other if they cannot be configured to perform equally. Combine this value with CV51 and CV52 to cater for different motor types - often very smooth running can be achieved by experimenting with these values, even on motors that are apparently jerky to begin with under DCC.
51 P-Value 0-255 (80) Optimises EMF characteristics. Modify this to adapt to specific motor requirements (proportional part).
52 I-Value 0-255 (40) Optimises EMF characteristics. Modify this to adapt to specific motor requirements (integral part).
64 Reference voltage 0-255 (100) EMF 100 = 20V track voltage
67-94 Free speed curve 0-252

Activated with CV29 bit 4 is set.

Default values: 9, 18, 27, 36, 45, 54, 63, 72, 81, 90, 99, 108, 117, 126, 135, 144, 153, 162, 171, 180, 189, 198, 207, 216, 225, 234, 243, 252

116 Shunting function (yard mode) configuration 0-255 (0)

Shunting mode may be switched on/off via appropriate function mapping - see CT extended function mapping document for more information

Only active if bit0-bit2 set

Bit 0 (1) - effects of CV3 and CV4 are disabled when shunting mode activated

Bit 1 (2) - maximum speed is halved

Bit 2 (4) - reverse is 65% of maximum speed (regardless of shunting mode) - applies from SW Version 40 or later

Bit 3 (8) - brakes with diode 4:1 is active - see also CV 162

Bit 4 (16) - brakes without diode

Bit 5 (32) - not used, must always be 0

Bit 6 (64) - means that the "Rangierfunktion" acts as a command button that is, that the automatic train control system (brake or diode and HLU) - (equivalent to the MAN key = manual)

Bit 7 (128) - short burst of idling, returning to normal speed

142 Short-circuit threshold 1 0-255 (90) Direct cut-off at overload of motor output
143 Short-circuit threshold 2 0-255 (80) Fast cut-off at overload of motor output
144 Short-circuit threshold 4 0-255 (70) Slow cut-off at overload of motor output
162 Sensitivity of the diode voltage 0-255 (10) See also CV116. Value of 10-20 is generally well tolerated, the smaller the value the more sensitive.

CVs For Function Mapping

There is an NMRA standard for mapping functions to buttons in DCC, and these are supported by the SL51-4 too. However, the standard only defines how the first few functions can be mapped, as it was developed before any decoders appeared on the market with many more functions. The SL51-4 provides 8 function outputs which can be used for things like lighting, smoke units, couplers/decouplers and just about any other electrical device you can dream up which could fit in the train.

The SL51-4 provides 4 function outputs ready-wired so you can just attach the wires directly to your lighting etc. as well as a further 4 function outputs provided via solder pads. A total of 8 function outputs then.

On top of these 8 physical function outputs (4 on the SL75), you also have the sound effects which you may want to control with the press of a button. There are up to 16 auxillary sound effects available for this purpose, plus you need a button to switch the main running sounds on and off. That's a fair few function buttons required! This means CT have had to provide some non-standard CVs to allow for a wider mapping range.

The 16 Sounds Effects are grouped into 2 banks of 8 (1-8 and 9-16) and only 1 of those banks is available at any given time. You can switch between which bank is used by activating the 'Alt' function, so essentially you need to dedicate a Function Key specially for the 'Alt' function. It is worth it though, as you can get to so many more Sound Effects!

A separate document is available for you to download from YouChoos which presents the CVs, the outputs and sounds, in a tabular format, with examples of what values you need to put into which CVs in order to get the desired mapping. Refer to the SL51-4 Extended Function Mapping document for a more detailed description (includes a link to a downloadable mapping table in PDF or DOC format). It is quite straight-forward once you have the table. You should note that some functions and sounds cannot be mapped to certain function keys - there are ranges that you can choose from, and this will become evident if you study the table.

I therefore will not spend any more time discussing how function mapping works, other than to list the CVs involved...

CV(s) Purpose Comments
33-46 NMRA standard function mapping These CVs follow the standard NMRA guideless for how CVs should be mapped.
163-176 CT extended function mapping

A combination of 33-46 and 163-176 provides full mapping of all the SL51-4's 8 function outputs and sound effects, as well as shunting mode and main running sounds. You really need to calculate the values for both ranges of CVs at the same time to map the functions properly.

Function Outputs, Effects and Related CVs

Let's now look at what CVs are available that have some influence on the physical function outputs, used for lighting, smoke units etc. We'll consider those CVs that are related specifically to coupling units a little later.

CV(s) Purpose Range (Default) Comments
13 Functions active in analog mode 0-255 Use bits 0-3 (possibly 0-7?) to determine which function outputs are switched on when operating on DC.
54 PWM dimming level for function outputs 0-255 (50) PWM for function output: specifies the level of dimming applied to any function output with dimming selected via CV 57. Note that any function outputs with dimming switched on have the same dimming level applied - they are not individually dimmable by different amounts. Useful for reducing brightness of lights, or level of smoke generator for example. CV54=50 means 50% power output on function.
57 Dimming mask 0-255 (0) Dimming mask: turns dimming (level defined in CV54) on and off for each function output. Each bit represents one function output, up to 8 functions (bit 0 for white wire, bit 1 for yellow wire etc.)
117 Function key for user-triggered Low-Beam dimming 0-12 (0) The CVs above (54 and 57) control permanent dimming of the function outputs e.g. if you always want a smoke generator to run at 50% power, use CVs 54 and 57 to achieve that. However, the decoders also support a Function-Key controlled dimming which we will call Low-Beam dimming here for the sake of convenience. When activated, it caused the outputs to be temporarily dimmed for a timed period before they return to their normal output level again. CV117 defines the Function Key that causes the Low-Beam effect to be applied. 1=F1, 2=F2 12=F12. See also CV118, CV119 and CV120.
118 Mask for function-key triggered Low-Beam dimming 0-255 (0) Controls which function outputs the Low-Beam action applies to. See also CV 117 and 119. Each bit represents 1 function ouput (0-3). 1 = white wire, 2 = yellow wire, 4 = green wire, 8 = purple wire, 16 = 5th output, 32 = 6th output, 64 = 7th output, 128 = 8th output
119 PWM dimming level for Low-Beam feature 0-100 (0) Controls the dimming level when the Low-Beam feature is activated. 50 = approximately 50% of full brightness, 100 = 100% i.e. no dimming. 0 also means no dimming.
120 Cycle duration of Low-Beam effect 0-255 (0) Defines how long the Low-Beam effect will last. See CVs 117, 118 and 119.
114 PWM low-point for lighting effects 0-100 (0) PWM for effects - some of the lighting effects chosen in CVs154-161 pulse between a high point and a low point. This CV specifies the level of the low point in those cycles
115 Flash cycle time 0-255 (0) Cycle time for flashing light effects, as specified by CV154-161
139 Short-circuit threshold 1 0-255 (15) Direct cut-off at overload of function outputs
140 Short-circuit threshold 2 0-255 (12) Fast cut-off at overload of function outputs
141 Short-circuit threshold 3 0-255 (10) Slow cut-off at overload of function outputs
154 Lighting effect for forward light 0-255 (0)

Output 0 (white wire)

0 - No effect

1 - Flashing

2 - Flash-pull

3 - Single pulse strobe

4 - Double Flashing strobe

5 - Headlight (brightness between maximum and PWM value in CV 114)

6 - Ditch light left (brightness between maximum and PWM value in CV 114)

7 - Ditch light right (brightness between maximum and PWM value in the CV 114)

8 - Rotary beacon (brightness between maximum and PWM value in the CV 114)

9 - Gyralite (brightness between maximum and PWM value in the CV 114) - can also be used for firebox glow

10 - Mars light

11 - Soft-start

12 - Brake sparks (short flash activated only when the loco comes to a stop)

For output when forward only, add 64 to the above value e.g. 1 + 64 = 65 flashing on Forward only. For output when in reverse only, add 128 to the above value e.g. 1 + 128 = 129 flashing on Reverse only. If neither 64 nor 128 is added, it is assumed that the effect should be active for both forwards and reverse.

CVs 155 -161 provide the same effects for each of the other function outputs.

155 Lighting effect for reverse light 0-255 (0) Output 1 (yellow wire) - see CV154
156 Lighting effect for function output 2 0-255 (0) Output 2 (green wire) - see CV154
157 Lighting effect for function output 3 0-255 (0) Output 3 (purple wire) - see CV154
158 Lighting effect for function output 4 0-255 (0) Output 4 (solder pad) - see CV154
159 Lighting effect for function output 5 0-255 (0) Output 5 (solder pad) - see CV154
160 Lighting effect for function output 6 0-255 (0) Output 6 (solder pad) - see CV154
161 Lighting effect for function output 7 0-255 (0) Output 7 (solder pad) - see CV154

Function Outputs, Coupler/Decoupler Related

CT decoders provide very good control for coupling units via function outputs. Here are the CVs which relate to this use of the outputs...

CV(s) Purpose Range (Default) Comments
55 PWM output level for holding of decoupler 0-100 (32) Represents the holding current for the decoupler i.e. the reduced power for holding after the initial uncoupling impulse (see CV56).
56 Decoupler pulse time 0-255 (60) Defines how long for the initial pulse on the decoupler at full power until it is reduced to the value defined in CV55. Time is set in 0.1 second units.
58 Dimming mask for decoupler function 0-255 (0) Defines which function outputs the decoupler functionality applies to. Each bit represents one function output.
147 Discharge of the coupling 0-126 (20) A kickback effect causing the locomotive to run backwards slightly - a tiny jerk of the motor to achieve uncoupling.
148 Away from wagons 0-126 (50) Speed when driving away from wagons, locomotive runs in the current direction, 126 = max. Speed under. Take into account the time set in CV3.
149 Discharge time 0-255 (10) The time for the unit pushed back. 0.1 seconds, 10 = 1 seconds
150 Drive away 0-255 (30) The time for driving away unit 0.1 seconds, 30 = 3 seconds
151 Selection of automatic disconnection 0-12 (0) 0 = off, 1 = F1 2 = F2 3 = F3, 4 = F4, etc.
152 Uncoupling mask forwards 0-255 (8) Select the function to be used, 4 = F2, 8 = F3, 16 = F4, 32 = F5, 64 = F6 128 = F7
153 Uncoupling mask backwards 0-255 (8) Select the function to be used, 4 = F2, 8 = F3, 16 = F4, 32 = F5, 64 = F6 128 = F7

Zimo Control System CVs

Also supported by CT decoders are various aspects of the Zimo control system. I don't claim to know anything about these, so presented here are simply direct translations of the text from the CT documentation (see also CV 137 'Special CV')...

CV(s) Purpose Range (Default) Comments
59 Signal controlled speed "L" 0-255 (168) Only available in ZIMO environment
60 Signal controlled speed "U" 0-255 (84) Only available in ZIMO environment
61 Signal controlled acceleration reaction time 0-255 (1) Only available in ZIMO environment
96 Zimo Signal controlled speed "FL" 0-255 (212) Speed selected between F-L (or MX9 HLU) is in version 52, see CV59, 60
97 Zimo Signal controlled speed "LU" 0-255 (126) Speed selected between L-U (or MX9 HLU) is in version 52, see CV59, 60
98 Zimo Signal controlled speed "U-Stop" 0-255 (42) Speed selected U-Stop (or MX9 HLU) is in version 52, see CV59, 60
138 Break time (HLU) 0-255 (3) Break delay for HLU section (for ZIMO systems only)

Using CVs to Affect Sound

Our final section on CVs will consider how the sound output can be controlled and affected...

CV(s) Purpose Range (Default) Comments
49 Configuration bits for sound 0-255 (0)

CV49=0 gives 4 cylinder steam engine

Bit 0 (1) - set if you use a Reed switch for wheel synchronising for steam engines - see also CV133=number of Reed Contacts - pulses per stroke e.g. CV133=1 means 1 stroke/pulse

Bit 1 (2) - set for Diesel or Electric loco - uses the AUTO slots - recommended approach for diesel/electric

Set both Bits 0 & 1 (value 3) for diesel and electric sounds that use Sound Slots 00 to 11 (must all be filled with sounds) - this is deprecated by the use of the AUTO sound slots (also known as Slots 1000-3000), so is not recommended.

Bit 2 (4) gives 2 cylinder steam

Bit 3 (8) gives 3 cylinder steam

Bit 4 (16) - no steam strokes during downhill/deceleration (only idle sound)

Bit 5 (32) - evaluate the LGB pulse from F1

Bit 6 (64) - play no sound between stand-still and running e.g. whistle (Slots 21-23 and Slots 24-26)

Bit 7 (128) - no sound between running and stand-still e.g. brakes (Slots 27-29 and Slots 30-32)

62 Braking threshold 0-255 (10) Braking threshold: indicates the number of speed steps that need to be reduced within 1 second in order for the rapid braking noise to trigger (Sound Slots 120 to 122). If the sounds are in three parts, the middle section is played in a loop until the delay is over.
104 Threshold braking end 0-255 (0) Braking sequences, CV104 = 50 brake sequence is between 25 to 24 of running outsourced (?). CV104 = 0, the sequence of the brake is automatic depending on the sequence of the brake adapted (?) (valid from SW Version 100) See also to CV62, CV107 - unsure of exact effect
107 Break threshold 0-255 (0) Brake threshold: triggering of final brake sequence sounds (Slots 27-29 and 30-32). CV107=50 triggers these brake sounds when speed steps from 25 down to step 24. CV107=0 triggers final brake sounds when speed steps from 1 to step 0 i.e. actually stopped (recommended - for example, final braking sounds where loco comes to an actual standstill).
108 Bitmask for enless manual sound 0-255 (0) ONLY operational when CV49 bit 5 is set. For use with LGB pulse chains.Bit 0 for sound 1; bit 1 for sound 2 etc.
110 Load-dependent sound variation: 1-15 (4) Set to 0 to give no load-dependent variation; then a range from 1 (high dependency) to 15 (low dependency on load). If configured carefully, this feature can be used to detect a heavy train, or unhill climbs and cause the sound (chuffs for steam) to use the 'acceleration' sounds under that load. However, beware - using an excessive value here will cause the train to produce unnecessarily loud chuffs at unwanted time e.g. travelling around a curve.
112 Random sounds at standstill 0-255 (255) Chooses which sounds may occur randomly while idling. Set to 0 for no random sounds at standstill or set bits 0-7 to control which sounds are included in random play (Effects 1-8). See also CV131. It is not possible to specify sounds 9-16 for random play.
113 Random sounds during motion 0-255 (255) Chooses which sounds may occur randomly while the loco is moving. Set to 0 for no random sounds while moving or set bits 0-7 to control which sounds are included in random play (Effects 1-8). See also CV131. It is not possible to specify sounds 9-16 for random play.
121 Volume for main sounds 0-63 (63)

Values depend upon software version:

Old versions have range 0-3 only (0 gives no sound, 3 gives maximum volume). Newer versions have range 0-63 (63 being maximum). Expect that future versions may range from 0-255.

122 Volume & Repetitions for sound effect 1 0-255 (3) Volume & Repetitions for sound effect 1 (Slots 37-41): bits 0-1 specify volume; bits 2-4 for number of repetitions of middle sound (Slot 39); bits 5-7 define number of repetitions of sound effect overall. If the 'Alternate' sounds are activated, this applies to sound effect 9 instead (Slots 77-81)
123 Volume & Repetitions for sound effect 2 0-255 (3) Volume & Repetitions for sound effect 2 (Slots 42-46): bits 0-1 specify volume; bits 2-4 for number of repetitions of middle sound (Slot 44); bits 5-7 define number of repetitions of sound effect overall. If the 'Alternate' sounds are activated, this applies to sound effect 10 instead (Slots 82-86)
124 Volume & Repetitions for sound effect 3 0-255 (3) Volume & Repetitions for sound effect 3 (Slots 47-51): bits 0-1 specify volume; bits 2-4 for number of repetitions of middle sound (Slot 48); bits 5-7 define number of repetitions of sound effect overall. If the 'Alternate' sounds are activated, this applies to sound effect 11 instead (Slots 87-91)
125 Volume & Repetitions for sound effect 4 0-255 (3) Volume & Repetitions for sound effect 4 (Slots 52-56): bits 0-1 specify volume; bits 2-4 for number of repetitions of middle sound (Slot 54); bits 5-7 define number of repetitions of sound effect overall. If the 'Alternate' sounds are activated, this applies to sound effect 12 instead (Slots 92-96)
126 Volume & Repetitions for sound effect 5 0-255 (3) Volume & Repetitions for sound effect 5 (Slots 57-61): bits 0-1 specify volume; bits 2-4 for number of repetitions of middle sound (Slot 59); bits 5-7 define number of repetitions of sound effect overall. If the 'Alternate' sounds are activated, this applies to sound effect 13 instead (Slots 97-101)
127 Volume & Repetitions for sound effect 6 0-255 (3) Volume & Repetitions for sound effect 6 (Slots 62-66): bits 0-1 specify volume; bits 2-4 for number of repetitions of middle sound (Slot 64); bits 5-7 define number of repetitions of sound effect overall. If the 'Alternate' sounds are activated, this applies to sound effect 14 instead (Slots 102-106)
128 Volume & Repetitions for sound effect 7 0-255 (3) Volume & Repetitions for sound effect 7 (Slots 67-71): bits 0-1 specify volume; bits 2-4 for number of repetitions of middle sound (Slot 69); bits 5-7 define number of repetitions of sound effect overall. If the 'Alternate' sounds are activated, this applies to sound effect 15 instead (Slots 107-111)
129

Volume & Repetitions for sound effect 8

or

Strong time (CV39 or older)

0-255 (3)

From SW version 40 onwards CV 129 has this meaning:

Volume & Repetitions for sound effect 8 (Slots 72-76): bits 0-1 specify volume; bits 2-4 for number of repetitions of middle sound (Slot 74); bits 5-7 define number of repetitions of sound effect overall. If the 'Alternate' sounds are activated, this applies to sound effect 16 instead (Slots 112-116)

Note that it is not possible to individually control the volume or looping of sound effects 9-16 (Slots 77-116) - they take on the settings for the equivalent effect in sounds 1-8.

Prior to SW version 40, CV 129 had the following meaning: Strong time: time that the acceleration chuffs sounds (Slots 0-3) continue after strong acceleration (0.5 seconds units).

130 Weak time 0-255 (4) Weak time - how long the deceleration chuffs (Slots 8-11)) should continue for after reducing speed (0.5 second units).
131 Random time 0-255 (20) Minimum time between 2 random sounds (0.5 second units). In practise it is the period always used between random sound - it is not a random duration.
132 Stroke Base at full speed 0-255 (100) Stroke speed at full speed: Time between 2 strokes/chuffs at full speed
133+134 Stroke Base at Step 1 (153/0)

Stroke speed at Step 1 (LOW byte in CV133, HIGH byte in CV134): time between two steam strokes at speed step 1 in seconds.

This can be a large number, so is defined using 2 CVs (133 and 134 with the LOW byte in CV133 and HIGH byte in CV134).

Calculated via the formula: K = 1476 / time (1476 is a constant always used for this calculation by the decoder)

Example 1: K=153 gives approximately 9.6 sec between chuffs

Example 2: if 20 seconds wanted between chuffs, so K = 1476 / 20 = 73.8 rounded to 74 gives CV133 = 74, CV134 = 0

Example 3: if 3 seconds wanted between chuffs, so K = 1476 / 3 = 492. Since K > 256 we need to use 2 bytes, so split low byte and high byte: 492 / 256 = 1.927875 thus CV134 = 1 (rounded down), CV133 = remainder i.e. 492 - (256 * 1) = 236

135 Frequency min 0-255 (128) Reduces the pitch of chuffs or engine sounds at lower speed steps. 128 is default pitch (sounds played as originally recorded). Use this CV along with CV136 to define how engine pitch or chuff pitch increases with the speed of the loco.
136 Frequency max 0-255 (128) Increases the pitch of chuffs or engine sounds at higher speed steps. 128 is default pitch (sounds played as originally recorded).
145 Activation of sound looping 0-255 (0)

If the corresponding sound function is activated, it will first play its 1st and 2nd Slots. After that, Slot 3 is repeated until the feature is turned off. After requesting off, it plays closing 4th and 5th Slots.

Bit 0 (1) - for looping of Sound 1 (Slots 37-41)

Bit 1 (2) - for looping of Sound 2 (Slots 42-46)

Bit 2 (4) - for looping of Sound 3 (Slots 47-51)

Bit 3 (8) - for looping of Sound 4 (Slots 52-56)

Bit 4 (16) - for looping of Sound 5 (Slots 57-61)

Bit 5 (32) - for looping of Sound 6 (Slots 62-66)

Bit 6 (64) - for looping of Sound 7 (Slots 67-71)

Looping for Sound effects 8-16 cannot be configured - they are not looping.

146 Strong time 0-255 (12) From SW Version 40 onwards, CV146 has the following meaning (used to be in CV129): Strong time: time that the acceleration chuffs sounds (Slots 0-3) continue after strong acceleration (0.5 seconds units).
177 Trigger for rapid acceleration 0-252 (40) Indicates the number of speed levels that must be attained within any 100 msec period in order to trigger the sound in Slots 123-125). If the sounds are in three parts, the middle part is played in a loop until the requested speed is reached. See also CV 107 for trigger to rapid braking sound.

Experiences & Commentaries

YouChoos Resouces

HINT: For document links below, either open them directly in your web browser by clicking the links, or right-click and save target instead...

YouChoos commentary on various decoders    
YouChoos Products

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  • CT SoundProg device (not supplied)
  • UK power supply (not supplied)
  • Serial-to-USB cable (can be supplied by YouChoos on request)
  • YouChoos' own software for creating, managing and loading sound projects to CT decoders (included in &25 license)
  • Full documentation (supplied digitally)

Download Software

Download Software

Anyone can try out this software for free by downloading the latest version from here. A license key is required to save projects, or to load them into a decoder.

User Guide

Download User Guide (PDF)

Download the User Guide for the YouChoos CT SoundProg application here.

Version History

Enhancements and Fixes

View Version History here, for a list of enhancements and bug fixes.

The YouChoos CT SoundProg application provides an easy-to-understand interface for configuration of CT Elektronik sound decoders, including an intuitive design for almost all aspects of the decoder's features - not just sound. Take a look at the screen shots below to get an idea of how powerful and simple this is...

Project details Edit individual CVs DCC loco address
Motor tuning and speed settings Function Outputs Steam sound schedule
Diesel/Electric sound schedule Callable sound effects Sound configuration
Function Key mapping Update decoder Firmware or load sound project