ORIGINAL: HarryC

The following is a quote from the Multiplex literature. Note that the error detection is done on each individual servo pulse and has nothing to do with needing subsequent frames to compare.

"A micro processor in the IPD receiver detects the control signals from the transmitter, checks them for validity, and then passes on the approved signals to the servos. To the IPD receiver "valid' means signals whose pulse width lies within the range 890 msec to 2350 msec. These limits are outside the normal range of most radio control transmitters, even those not made by MULTIPLEX.
If invalid signals are picked up, the receiver blocks them, and passes on to the servos the last received valid signals. It continues to do this until it picks up "good' signals again, or until the time limit of 0.5 seconds has elapsed. This behaviour corresponds to the HOLD function familiar to any PCM user.
If the IPD receiver picks up no valid signals for a period longer than 0.5 seconds, it can pass a programmable safety position (fail-safe position) to the servos."