that both sticks are centered and the spacing between pulses is 1.5 ms.

When the first pulse, the start pulse, is received it will only turn on the Chan 1 flip-flop. The chanel 1 flip flop is conditioned to turn on by the fact that the lock out timer is on. Chan 2 through 4 will not turn on because none of the previous channels are on. Also this pulse will reset the lock-out timer and its output will be off. Now 1.5 ms later the second pulse is received. This is the pulse which defines the end of channel 1 and the start of channel 2. Since the lock-out timmer is now reset, the only chan flip-flop conditioned to turn on is the Chan 2 flip flop. Also since the channel 1 flip flop is on and the lockout timer off, the channel 1 flip- flop will be turned off. The lock-out timer will  be reset again with this pulse even though it hadn't turned back on.

What we now have is that the channel 1 output to the servo was on for 1.5 ms. and we have just turned on the channel 2 flip-flop.

Now 1.5 ms later we will receive the third pulse. This is the pulse defining the end of channel 2 and the beginning of channel 3. Since the lock-out timmer is still reset, the only chan flip-flop conditioned to turn on is the Chan 3 flip flop. Also since the channel 2 flip flop is on and the channel 1 flip-flop is off, the channel 2 flip- flop will be turned off. The lock-out timer will be reset again.

What we now have is that the channel 2 output to

the servo was on for 1.5 ms. and we have just turned on the channel 3 flip-flop.

This sequence will repeat itself through all four channels.

Now, if you recall when we were discussing the encoder operation, we stated that the last channel pulse was followed by a reset period which was required by the decoder. The reset period is a period of time long enough for the lock-out timer to return to its on position. This must occur before the next frame of pulses is received. This period would be longer than the maximum time between pulses, longer than 2.0 ms, and yet short enough to ensure that it was reset before the next frame of pulses was received. A typical period would be 5 to 6 ms which would allow the dropping of a single pulse without reseting the unit. When the lock-out timer resets, it resets any flip-flop that for some reason was on. This ensures that if we had lost a pulse in the transmission, that a channel flip-flop was not left on. This also ensures that we will "sync" the receiver to the transmitter within one frame after turning on the equipment.

Remember this article is for your information only and is not a design, service, or operational manuals. Although I have tried hard to present accurate data, it comes with no guarantees.

For what it's worth--Al Coelho

Figure 2 - Encoder timing