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Tx20Sv2 User Information

Tx20Sv2 is a hand-held wireless transmitter intended to control one model railway live steam locomotive or a battery electric locomotive with the ESC set to low-off throttle. Tx20Sv2 has a large knob for regulator control plus a smaller knob for valve gear (or ESC direction control) and three push buttons for auxiliary functions (e.g. a whistle servo).

Tx20Sv2 can be used for Micron and Deltang receiver programming using the reverser control to step through programming levels. Programming details for each receiver may be accessed from the web page for the receiver.


Control R/C Channel Channel Value
regulator knob:1
F1 button:2 button up = mid, button down = low
direction knob:3
F2 button:4 button up = mid, button down = low
bind/F3 button:5 button up = high, button down = low


The Tx20Sv2 uses a PP3 9V battery, preferably Alkaline or NiMH / Lithium rechargeable. The maximum working voltage of the internal electronics module is 10V and there is a protection diode wired in series with the battery lead. This allows the battery voltage to be up to 10.7V. If the battery voltage is above this value, the internal regulator will shut down and the transmitter will not operate.

To replace the battery:

On / Off Switch

Tx20Sv2 has a 2-way latching toggle switch for power and adjacent LED indicator on the top panel. The power is on when the switch toggle is down - i.e. pulled toward the front. The LED lights continuously when the transmitter is on and flashes when Tx20Sv2 is in bind mode (see below). It is best to switch the transmitter on before the receiver. If a receiver is switched on with Tx20Sv2 off, it is likely to enter bind mode with rapid flashing of the LED on the receiver board. If you did not intend to bind, switch the receiver off, then switch Tx20Sv2 on followed by the receiver.

Regulator Knob

The regulator control is low-off with no centre-click and operates R/C channel 1. Off/Stop is at the fully counter-clockwise rotation (left/CCW) of the knob and speed increases at the knob is rotated clockwise (right/CW).

Direction Knob

The direction control has a centre-click and operates R/C channel 3. It is typically used to control a servo connected to the loco reversing gear. If used with a receiver that has built-in ESC, the receiver must be configured for 'low off', full-range motor control.

F1 & F2 Push Buttons

The two auxiliary function push buttons F1 and F2 may be used to control lighting, couplers, sound cards, etc. All model rail receivers available from Micron can be configured with momentary (press for on, release for off) or latching (press for on, press again for off) outputs that may be operated by F1 or F2.

Bind Button

If a receiver has not previously been bound, it has to be 'paired' with the transmitter. Binding is only required once per receiver.

  1. Put your receiver into Bind mode (if a Micron or Deltang receiver, switch it on and wait for the LED to flash fast).
  2. Press and hold the Bind push-button on the transmitter.
  3. Switch the transmitter on by pushing the Power button and then release the Bind button.
  4. Binding is complete when the receiver LED stops flashing.
During normal operation, the bind button can be used as an auxilary control - e.g. horn or whistle sound trigger. TAKE CARE to avoid holding the bind button down for 20 seconds or more as this will cause the transmitter to enter calibration mode or reconfigure some of the controls.

Receiver Programming

You need to refer to the receiver's programming instructions for details of the available functions and the programming sequence to modify the functions.

The universal method of putting Micron and Deltang receivers into programming mode requires R/C channels 2 and 4 - buttons F1 and F2. The alternative method is to tap out Morse ‘SOS’ on the Bind/F3 button.

To Enter Programming Mode using F1 and F2:
  1. Centre the direction knob
  2. Switch the Tx on and hold down both F1 and F2
  3. Apply power to the Rx and its LED will start rapid flashing
  4. Release F1 and F2
    The Rx LED will now show a 1-flash – this is a repeated single short flash followed by a longer pause. This first flash pattern is called the 'Menu' in the programming instructions.
To Enter Programming Mode using the SOS method:
  1. Centre the direction knob
  2. Switch the Tx and Rx on and wait for the Rx LED to stay on solid; you should now have normal control of the model
  3. Wait at least 5 seconds without touching any controls
  4. Tap out the morse code ‘SOS’ on the bind button (… --- …)
  5. If the SOS pattern is recognised, the Rx LED will display a repeating single-flash (1-flash pause and repeat)
  6. If you do not get the 1-flash, go back to step 3 and repeat the SOS
  7. Switch the Rx off at any time to abort
To make changes to receiver settings:

One programming change requires up to five choices to be made. These are called 'levels' and each has several options. They are documented in the programming table for the particular receiver; the Micron web page description for a receiver contains a link to the programming table for that receiver. Completion of a programming change exits programming mode and requires the F1/F2 or SOS method to be entered again for the next change.

You have to remember which level you are changing and the repeating LED flashes display the current option for that level. It is a good idea to write the programming sequence on a piece of scrap paper and cross off each digit as it is entered. You always start at level 1. For example, the first choice is the Menu number (programming group). The first option (1-flash) is for changing 'H' (ESC) outputs, the second (2-flash) is Menu 2 to change P outputs for servos, 3-flash is for Menu 3 to change P outputs for on/off switching, etc. Refer to the Programming Table for your receiver to find the number of options and what they change. Each level is in a separate column, 1 to 5 left to right.

For example, to configure a Deltang Rx6 receiver output P4 to switch on (3.3V) when F1 is pressed (R/C channel 2 is low), the programming sequence is 3,4,1,2,1, where:

3 = Menu 3
4 = P4
1 = momentary on/off
2 = R/C channel 2
3 = output idle 0V, 3.3V when channel is high (F1 pressed)

The general procedure for entering a programming sequence is, for each level:

When you make a choice with the direction knob (Fwd or Rev), the Rx LED will briefly flash rapidly and then the LED will:

Changes are saved automatically when the Rx LED lights solid at the end of a programming sequence. If a mistake is made mid way through a sequence, switch the Rx off to abort.

Repeat the above steps for each program function that you wish to alter.

For example, to set the ESC output (the first if the receiver has multiple ESC) to respond to full range regulator on channel 1 and direction control on channel 3, the programme sequence is 1,1,2,1,3:


All ready-to-use transmitters are calibrated as the final manufacturing step. This normally only needs to be done once. If you suspect that the regulator control is not operating correctly or you have replaced any of the internal components (e.g. regulator potentiometer), your transmitter may need calibration.

If the bind button has been inadvertently held down for longer than 20 seconds, the previously stored calibration data will have been overwritten and you could find that the regulator control behaves strangely.

To perform calibration:

The Tx is now calibrated.