Non Toggling -- Characteristic of controls.

When controlling any device, it is nice for the control to be Non Toggling, or more technically "Idempotent". When one device is controlling another, it is easiest to provide a separate command for one state and another for another state. In contrast, the control may be Idempotent, or Toggling, such that you must know prior state or otherwise observe the device to determine what state it is in.

The typical example is the old push-button foot switch to control high-beams in some cars is toggling (not idempotent), as one time pressing it makes the lights bright and another time, it makes them dim. You have to look at the light to know what the current state is. In contrast, the multi-purpose lever approach is not toggling, as forward usually means high-beams and back is low beams.

Here are some other examples:

There is an important trait that you must also check when you consider using the Feedback Media Platform or Universal Bio Interface with a given Player. For best results, the action of PAUSE and PLAY must maintain their function regardless of their prior state. This is the trait we need in control of your Player as the FMP or UBI can't really see whether the player is working, it has to rely on knowing that a command will work the same time every time.

You can test your Player for non-toggling as follows:

1. Press PLAY and observe the player playing.
2. Press PAUSE, it should pause the player.
3. Press PAUSE again, it should not start to play. If it does, the player FAILS THIS TEST!
   Note: It is OK if pressing PAUSE again and again causes it to single step, as long as it does not start to PLAY.
4. Press PLAY, it should transition to playing.
5. Press PLAY, it should continue to play. If it pauses, IT FAILS THE TEST!

If your player only plays when the PLAY command is sent, and only pauses when the PAUSE command is sent, then it is Non Toggling, or "Idempotent", and you can use our interfaces without any difficulty.

Some players will partially pass the above test. For example, if PLAY causes PLAY always, but PAUSE toggles, it will be OK to use this equipment with some minor reduction in compatibility. If you are buying new equipment, be sure to buy only fully Non Toggling players!

See Player Compatibility Guide for a list of players that we've tested for Non Toggling.

-- Raymond Lutz - 08 Jun 2004