Rx6x Features (v602/603)


This page describes Rx6x features in some detail. Each feature has a 'keyword' (marked in red) which makes it easier to refer to. These receivers have some 'depth'. You are not expected to use every feature and receivers come with settings that meet common needs. But when you want to add a new feature like controlling lights or using different sticks for functions, the flexibility is there.


This Rx is compatible with DSM2 and DSMX transmitters. Most joysticks, switches and knobs on hobby transmitters control separate 'channels'. These are numbered and have some common names which are referred to below (eg: Ch1 Throttle). All outputs on the Rx can be used with any channel.


The Rx is designed to operate from 3-16v DC. This allows it to be used with many battery combinations. 1S, 2S and 3S lipos are common choices (3S = 3 cells in series).

The motor output (H1) can supply up to 1.5A when the motor is stalled at 100% throttle.

There are no minimum or maximum battery capacity requirements (mAh).


The Rx can be powered from rail track power including DCC. A bridge rectifier is needed on the train to handle AC or reverse DC polarity. A capacitor is needed on the train to reduce brownouts/LVC (5-flash on Rx). A regulator is needed if track voltages exceed 16v.


The Rx has an integrated forward/reverse motor controller for brushed motors (ESC). With this setting, one channel is used to control the motor in both directions. Center is off. Any channel can be used. Rx6x-2 has this setting for Tx21. Rx6x-3 is more suitable for joystick Tx's.


This option uses two channels to control the motor. Full stick movement of one channel is used to control the power level regardless of direction. Low is off. Any channel can be used. Rx6x-1 has this setting and is suitable for Tx21 and any joystick Tx.

Forward/reverse direction is set with a second channel. Direction can only be changed when the power is off. If the Direction channel is a self-centering joystick you simply push it in the required direction and let the stick center again. If it is a 2-position switch like on Tx21 it is toggled and left in the required direction.


Standard servo output instead of motor. The output pulses will be at battery voltage so may need to be reduced using an external 3.3-5v zener diode and resistor. This option is used to create Rx61-8 which has 8 servo outputs.


The power level can be made to go quicky to a minimum level as the throttle is opened. It can be set to 0 to 100%. The default is 0%.


The maximum power level available at full stick can be reduced to match engine speeds for a consist. It can be set to 0 to 100%. The default is 100%.


The motor's direction of rotation can be reversed using a programmable setting. This may simply be for convenience or to make a temporary change to suit a push/pull consist.

Another way of reversing the motor direction is to place the throttle at max before the Rx is switched on. The motor's direction will toggle each time you do this.


Motor speed is regulated with PWM. The PWM frequency can be adjusted to change motor torque, smoothness and the sound it makes. 60Hz is the default for most receivers. 60Hz and 250Hz are are fine for most motors and are in the range used by most traditional mains-powered train controllers. 15Hz is more suitable for some boats and it makes a 'pop-pop' sound. The 2kHz and 16kHz settings must only be used at very low currents (<400mA) and low voltages (<8.5v) and only if the Rx stays cool.


Softstart smooths changes to motor power. By default it takes a little under 0.5s to go from 0 to 100% throttle. This can be made more or less responsive.


Lipos are damaged if over-discharged. The Rx cuts power to the motor when the voltage falls too low. Power can be applied to the motor again if the operator first closes the throttle. Recharge your battery when this happens. Cut-off levels for voltages measured when the Rx was switched on are:

3v for <4.3v measured at startup
4v for 4.3-6v
6v for 6-9v
9v for >9v


If an external voltage booster powered with a 1S lipo is used, the Rx can monitor the lipo's voltage if the booster does not do this. The Rx will cut power to the motor when the lipo voltage falls to 3v. More details.


The Rx is compatible with:
- DSM2 'Air' transmitters
- DSMX 'Air' transmitters
- DSM2 'Surface' transmitters (steering wheel/throttle trigger)


The Rx has to be 'paired' with your Tx. This is called Binding. You only have to bind once. Your Tx can be bound with any number of compatible Rx's. The Rx can only be bound with one Tx at a time.

Auto Bind: The Rx will enter bind mode about 22s after being switched on. The led will flash fast. You then hold the bind button in on your Tx and switch the Tx on. The led should flash for a few seconds and then come on solid. Job done. If a bind signal is not detected within 1 minute, the Rx will exit bind mode.

Manual Bind: If this option is enabled, you have to connect the two pads together and then switch the Rx on. The Rx will enter bind mode immediately. The led will flash fast. Remove connection between pads. Same procedure with Tx as above.


The Rx will go into sleep mode to save power if the throttle is not changed for an extended period of time. The time to enter sleep mode can be set between 1 and 6 hours or 'never' (sleep disabled). The default is 1hr. The Rx has to be switched off and back on to use it again. The Rx draws 1mA in sleep mode.


The normal behaviour of the Rx on signal loss is to stop the motor. It holds the last known throttle position for 1 second and then closes the throttle smoothly over another 3 seconds. This can be reduced to 1s for a quicker response. Switching the Tx off is one way of invoking an emergency stop. Control can be restored by switching the Tx back on.

When the Rx is controlling a train on a continuous loop, it can be made to continue running in two ways:
(1) When you deselect the loco using the 'Selecta' feature, Rx6x-22 receivers are configured to 'continue' running. They will stop if the Tx is switched off (emergency stop).
(2) When you set failsafe to the SLEEP time. If the Tx is switched off the train will continue running until the sleep timer expires (eg: after 1 hour). If the sleep time is set to 'never sleep' the train will continue running forever. Control can be restored by switching the Tx back.

In all cases, if LVC (low voltage cutoff) is enabled the LVC function will stop the motor when the battery reaches the minimum voltage.

[LED2] - LED2

The led on the Rx often reveals the state it is in. If the Rx is concealed in a model and another led is being controlled by one of the 'P' outputs, the Rx's led activity can be mirrored on that other led. This mirroring only occurs up until the Rx become Armed. Once armed the 'LED2' activity stops and the normal activity of that output commences.


This is a standard servo output. The position of the servo is proportional to the position of the controlling channel. It can control a servo or external ESC (eg: brushless). Rx61 has a 4v BEC to power a small servo.

There is a slow-motion option. This is intended to be used when operating a coupling with a switched channel (eg: Ch5 Gear). This gives the operator time to check that the coupling is not jamming.


This feature gives full servo movement from a half stick movement on the Tx. It is intended to operate a coupling with a self-centering joystick where mid-stick is the closed position for the coupling.

The servo is at one extreme when the stick is centered (coupling closed). The servo moves to its other extreme in a proportional manner as the stick is moved (eg: to the right) to open/release the coupling. The servo returns the coupling to its closed/locked position when the stick is centered. The servo does not move when the stick is moved the other way.


This feature provides two servo type outputs whose controlling channels are mixed. It can be used to operate two servos or two external ESC's (eg: differential thrust steering for tank, digger, boat, blimp, etc).


A brake light can be made to come on automatically when the throttle is closed. The time that the led is on for can be adjusted from 1-6 seconds with the [BR_ON] setting. The brake light also comes on if the Rx is receiving a signal but is prevented from being armed because the throttle is not closed.

A reversing light can be made to come on automatically while the throttle is in the reverse position.


Two outputs can be configured for left/right indicators. The Activating Channel (eg: Ch4 Rudder) represents the stalk/switch used on a motor vehicle. The Steering Channel (eg: Ch2 Aileron) is the channel used for steering the vehicle. Only the Activating channel can start the indicators flashing. Both channels can cancel them.

The 'trim' on the Tx for the Steering channel often has to be used to make the vehicle run straight. In order to have a true center/narrow deadband for cancelling the indicators, the position of the Steering channel is detected automatically each time the Rx is switched on.

A quick movement of the Activating channel left or right (<2 seconds) starts an indicator flashing. A movement to the Left held for >2 seconds makes both indicators flash as Hazards. The same movement cancels the Hazards.


One output can made to flash rapidly to simulate an emergency light. If Indicators are enabled, the Flasher must use the same Activating channel. A movement to the Right held for >2 seconds starts or stops the Flasher.


Outputs are ON while the Tx stick/switch is deflected. Each channel can control two outputs (1 'left', 1 'right'). Both are OFF at center.


Outputs toggle ON or OFF each time the Tx stick/switch is deflected. Each channel can control two outputs (1 'left', 1 'right'). Each output latches ON or OFF until the stick is deflected after having been centered.


This feature is the same as above except that the time a channel is deflected can be used to operate two outputs each way. Each channel can control four outputs (2 'left', 2 'right'). One output on each side toggles ON or OFF each time the Tx stick/switch is deflected for <2 seconds. A second output on each side toggles ON or OFF each time the Tx stick/switch is deflected for >2 seconds.


The position of all channels can be output on 1 pad to feed another module. It uses RS-232 async serial, 8 bit, no parity, 2 stop bits, LSB first. 3 speeds are available (125kb, 250kb and 500kb). Serial outputs normally occur every 22ms but cease for about 66ms every 1sec while the Rx does something else.

1. The first 2 bytes are used to indicate the start of a sequence. Their values are 0xFE and 0x02.

2. The data feed then contains 2 bytes for each channel in numeric order. These contain the channel position in a 10 bit form (0-1023) with no channel number indicator. The feed provides data for every Tx channel up to 10 but no less than 7 (even if not relevant).

3. Channel data is followed by 1 byte voltage indicator in tenths of a volt (eg: 36 is 3.6v). It should be accurate to 0.1v but is not calibrated. The maximum valid value is 175 (17.5v).

4. There is then a 1 byte signal strength indicator (RSSI) which has a 0-31 scale.

5. The final 1 byte is a checksum and is the sum of all other bytes cast to 1 byte.


'Selecta' allows receivers to be made active or inactive from the Tx. This allows you to expand the number of functions controlled using two or more receivers, or lets you hop between several models bringing them in and out of service without touching them. This is done by associating each Rx with a position on an activating channel. See video.


The position of the activating channel is memorised during binding. The Rx responds to the Tx only when the activating channel is in that position. A 'switched' activating channel is the most convenient. But the 'trim' on a joystick channel can also be used to select up to 5 models. Tx22 is designed specifically for trains and has a 12-position 'loco selector switch'. More details.


The normal and safe behaviour when a model is made inactive is for the motor to stop. When the model is something like a train on a continuous loop, the 'continue' option can keep everything running while you use the Tx to control another Rx. More details.


Two Tx's can be associated with each model. If you flick the switch, the motor in the current active model will stop and it will seek out the other Tx. The 2nd Tx will have to accept the model to take control. More details.


This option is only relevant to Tx Change. More details.


'Programa' indicates a capabilty for changing settings in the Rx with a handheld programming device. You make choices on the programa device and press a button to update the Rx at any time. Settings can also be changed using a hobby Tx. The structure for all changes are Programming Options (Rx61).

PROG1 is a converted receiver. The pins are used to make the led flash for each programming option. The button is used to transmit the changes. More details.

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