RC4 Predecessor - Relic Fail-Safe Module

This is simply a historical representation of RC4's lineage. The original idea that eventually led to the development of RC4 began somewhere in the early 1990s. It consisted of some discrete integrated circuits (chips) and was designed to do one specific task: provide fixed signals to four servos in the absence of any input signal from an R/C receiver.

The prototype for this device was very bulky and consisted of six chips mounted on two separate prototyping boards that were joined together using stand-offs. Here are some photos:

Here is side 1 of the prototype:

Side 1 primarily consisted of the logic circuitry necessary to detect the presence or absence of an input signal from an R/C receiver. It controlled the circuitry on side 2 and determined whether to drive the outputs from the input signals or from the fixed signals generated on-board.

And here is side 2 of the prototype:

Side 2 contained the circuitry that generated the four fixed signals that were to drive the servos in the absence of input signal. The four blue rectangular components seen in the image are the trimmer resistors that were used to set the pulse width for each of the four fixed output signals. Obviously, setting appropriate signal values for a specific application required some manual intervention until the signals were where I wanted them.

It was a very crude device and a very crude solution to my problem. It lacked any interesting features, and wasn't very flexible. Fortunately for my airplanes, this crude device never flew in any test flights. But to see it next to RC4 provides a sense of how far things have come since then (or, at least how far I have come since then).