Step 6 : The Receiver


The DS9637 is a Schottky dual differential line receiver. It will take your pair of inputs (one normal and one inverted), invert the inverted line back to normal and combine the two signals together.

Step 7 : The secret


Here's the trick: When your inverted signal is inverted back to it's normal state, the noise on that line is inverted too. When the two signals are combined, the normal noise and the now inverted noise cancel each other out. Presto! A clean buffered copy of the input signal at the transmitter. I have successfully driven signals to my 595 controller from over 100' away with no data errors.

Step 8 : The Diagrams


Sounds like a complicated circuit but it's not. In fact it couldn't be easier and cheaper to build. Here is the schematic for the transmitter. Two chips and two caps. If you include the perf-board, it's about $2.50 worth of parts.

Step 9 : The Diagrams


Here's the schematic for the receiver. This has the same parts count except for the added resistors. Place a 100 ohm resistor across the pairs before they enter the receiver chip. This 100 ohm termination of the line is to make sure the impedance of the pair matches the specifications of the chips.

Step 10 : That's it!!


There you have it. An extremely simple, reliable, and cheap way to make sure your signals stay clean. All for under $10. Not a bad deal. You can make a complete receiver/transmitter set on one general purpose PC board from Radio Shack (part number 276-159). Build it all at once, snap the board in half, and away you go.