Not strictly true Gary.

My Hunter uses two channels to sequence the doors and gear and it is all done using the TX, which in my case is a Futaba 14mz. But the sequencing can also be done using other high end TX's such as JR DSX12 or Futaba 12 FZ and, of course, the new 18mz.

To answer the original question there are basically three different ways to achieve the sequencing

1. Mechanically, I have a BVM Super Bandit and the gear doors are sequenced using a clever mechanical setup that utilises 2 valves, one for the gear and another for the doors. This method only uses one channel.
2. Sequencer. This is way Gary was referring to and the sequencing is done using a sequencer. Only one channel is used. The Jettronic unit is popular but there are others such as the relatively new units that are sequencer/valves/failsafe all in one unit.
3. TX Sequencing. This is becoming popular as you don't need any extra electonics in the model. The disadvantage is that it uses two channels but as you can have radios with 12-18 channels then thats not an issue these days. Of ocuse thinking about it, another disadvantage is that if you don't own a TX that can do this then is a bloody expensive to upgrade!

As Dave said, Tell us what you're trying to achieve, what radio you are using and then we can suggest a way of acheiving your end game.

Geoff.