Selecta - v611


Selecta allows receivers to be made active or inactive from the Tx. For example, several locos can be brought in and out of service without touching them. This is done by associating each Rx with a position of a selecting channel. Simply change the switch position to change which model is active. Selecta is enabled by default on '22' variants of DT receivers. These receivers simply require binding with Tx22 to enjoy this feature. Selecta can be enabled manually on other Rx6x receivers. An easy way is with 'paperclip' changes.


The position of the selecting channel is memorised during binding. The Rx responds to the Tx only when the selecting channel is in that position and the led on the Rx will come on solid. If the position is not correct, there will be a 2-flash and no settings on the Rx can be changed.

As soon as a model is deselected, its settings are frozen. 1 second after the Selecta switch stops changing, the next model becomes active. The 1s period can be reduced. This allows some 'fumble' time during which the throttle needs to be positioned where you want it. If the motor needs to change speed, it can take up to 3s to blend into the new position.

The selecting channel is designed for use with a 12 position rotary switch. One channel is normally dedicated for this purpose. Any channel can be used but DT products use Ch2. Each 'position' is about 12 'trim clicks' wide so the Trim on a joystick channel can usually be used to select several models.


The number of led flashes on the Rx reveals the current state:
1-flash - scanning for Tx on startup.
2-flash - the activating switch is in the wrong position for this Rx.
5-flash - low voltage.
Fast flash - Binding.
ON solid - all OK You have control.


The default action when a model is no longer selected is for it to 'hold' last known positions (ie: 'continue'). This is suitable for locos on a continuous loop or any scenario where you stop the model before deselecting it. If this behaviour is not appropriate, it can be changed to force a 'stop' when the model is no longer selected.


Receivers can remember different bind info for each Selecta switch position. This allows:

1. Control to be passed from one Tx to another.
(eg: if a loco is bound to Position 1 with Tx 1, and to Position 2 with Tx 2, control passes from one Tx to the other based on the switch position).

2. Locos controlled individually and in a consist.
(eg: if Loco 6 has been bound with Positions 6 and 7, and Loco 8 has been bound with Positions 8 and 7, they can be operated individually with positions 6/8 and together with position 7).

3. For programming.
People who normally use transmitters that are not intended for programming (eg: Tx22) can use one position for a transmitter which is suitable (eg: Tx20 or a joystick transmitter). This removes the need to rebind every time you want to make a change.

You normally just switch the Tx and Rx on and wait a few seconds for them to connect. The led will come on solid or display a 2-flash.

To select or deselect a model where both use the same Tx, simply move the Selecta switch and wait for them to connect.

To transfer control between transmitters:
* On the second (receiving) Tx, move the Selecta switch to a position that has previously been bound with the Rx.
* On the first (current) Tx, move the Selecta switch to the same position as above.
* Wait for the led on the Rx to come on solid and confirm that control has been passed.


Transmitters use different frequencies every time they are switched on. Once the frequencies for an operating session are known by each Rx, transfers between transmitters become very quick. Once the Rx finds the frequencies the Tx is using, it locks on to those and becomes 'connected'. The led will either be on solid or display a 2-flash. When the Selecta switch is placed in a position associated with another Tx, this forces the Rx to scan all the frequencies to find the other Tx. The led will flash once every 2s while it does this or connect quickly if the frequencies are known.

The tasks performed by the receiver at startup have a degree of complexity:
1. The Rx will scan all frequencies to try find the Tx that last used it. The led flashes once every 2s while it does this.
2. If it does not detect a signal within about seven seconds, it will search for the 'next' Tx that has been bound to it.
3. It will try to find three transmitters and then enter bind mode (rapid flash). The Rx normally only needs to be bound once. So if binding has previously been done, make sure the Tx is switched on and try again to connect. 'Try again' means either switch the Rx off and on, or wait for it to exit bind mode. The Rx only enters bind mode once per startup and exits automatically.
4. If the Rx exits bind mode automatically without binding (after 30s) it will then continue searching for all bound transmitters (up to 12) until it finds one.

The correct way to transfer control between transmitters is described above. If a different sequence if followed, several scenarios exist when the switch is moved on the Tx that has control:
1. Same Tx: If the new position has been bound with the same Tx, the led on the selected Rx will stay on solid and the first Tx will keep control.
2. No Tx: If the new position has never been bound with another Tx, outputs hold their current positions ('cruise control') and there is a 2-flash.
3. Different Tx: If the new position has been bound with another Tx, outputs will be stopped to perform a safe handover. The Rx will search for the second Tx:

3.1 If the second Tx is switched on and its Selecta switch is in a position that has been bound with the Rx, control will pass and the led on the Rx will come on solid. This is the 'correct' approach described above.

3.2 If the second Tx is switched on and its Selecta switch is in a position that the Rx has never been bound with a Tx, control will pass and the led on the Rx will display a 2-flash. This is the same as point 2 above. Move the Selecta switch to a position bound with the Rx to accept it.

3.3 If the second Tx is switched on and its Selecta switch is in a position bound to the first Tx, the two Tx's will keep pushing the Rx to the other Tx and the led on the Rx will probably stay off.

3.4 If the second Tx is not switched on (or does not exist because it was a Tx used for testing before delivery), the led on the Rx will flash once every 2s while it scans for the Tx. After about 7s it will scan for the first Tx again. If the Selecta switch on the first Tx is still in the position for the second, it will try to find the second again for another 7s. If you return the Selecta switch to a position bound to the first Tx, the first Tx will regain control. Position 6 is always used with a test Tx during manufacture.

As described in point 3 above, the motor is cut when a new Selecta switch position is selected which is associated with another Tx. When a Tx gains control (Rx led on solid), there is a transition process. There may be speed blending to match motor/throttle settings. The motor may need re-arming by closing the throttle.

'Tx change' adds a layer of complexity to Selecta. It can be disabled with programming or 'Paperclip' changes.


Selecta is intended for use with a 12-position rotary switch with Tx2. The switch and its resistors set the position of a controlling channel. Channels can have 1024 positions, 0 to 1023. By default, Selecta position '1' is between 236 and 283, position '2' between 284 and 331, position '12' between 678 and 819, etc. This allows for measurement jitter and manufacturing tollerances. Position '0' also exists between 0 and 235, and position '13' between 820 and 1023. Although only positions 1-12 are normally used, 0-13 should be available. This is mainly relevant for joystick transmitters or anyone who wants to use the higher and lower parts of the channel range.

Bind information is saved separately for each Selecta switch position to allow 'Tx Change'. When 'RS232 Bind' becomes available, 16 bind profiles will be exposed. 0-13 are as described above, 14 is used for Prog1/2/3, and 15 is a temporary holder for the most recent Bind because the Selecta position is only known after binding.

Selecta is intended to be controlled with Ch2 when used with Tx2. Tx2 has a calibration procedure for Ch2 to 'center' the measurements using switch position 6. When 'Menu 4' in the programming table becomes available, it will also be possible to 'learn' switch positions. This will change the default values associated with each switch position mentioned above. The Learn feature is not needed when using the 12-way Selecta switch with resistor values recomended for Tx2/Tx22.

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