Encoder And Decoder Comparison

Encoders and decoders are an ideal way of sending on / off data, such as button presses, to a remote location. When a line on the encoder is taken high, it will create a data stream that is sent to the decoder. The decoder will interpret the data stream and take a corresponding data line high to replicate the state of the encoder. This document gives an overview of encoder / decoder ICs and explains the differences between Linx encoders and decoders and those offered by other manufacturers.

WHAT IS AN ENCODER / DECODER?
Encoders and decoders are designed to transfer the status of an input such as a switch or contact closure over a wireless link. The encoder encodes the status of an input(s) into a Pulse Width Modulated (PWM) or serial data stream intended for transmission via an RF or infrared link. Once received, the decoder decodes, error checks, and analyzes the transmission. Often, address or ID information will be included for uniqueness and / or security. If the transmission is verified, the decoder's output lines are set to replicate the status of the lines on the transmitter.

A BRIEF HISTORY
The early days of encoders and decoders were dominated by fixed-address devices such as those offered by Holtek. Who doesn't remember a car fob or garage door remote with its formidable bank of DIP switches that were hopefully set to some reasonably unique address (and perhaps changed when your neighbors garage opened too!)? Then came the broad recognition that a transmission could be captured and later used to compromise the system. "Code grabbing," as the process was called, seemed to capture the grim specter of a robber crouching in the bushes waiting for you to press your remote so the transmission could be captured and used by a thief at a later time.

A solution to this very real, but perhaps over-hyped, threat was provided by Nanoteq of South Africa who developed the Keeloq encoder / decoder, which focused on security and utilized encryption to guard against code cracking or grabbing. In November 1995, Microchip Technologies, maker of the popular PIC microcontroller, acquired the Keeloq and became the sole owner of the technology. Today, this product dominates markets requiring high security, but fixed-address technologies continue to co-exist because of several advantages, which we will outline later. The entrance of Linx Technologies into the encoder / decoder market represents another milestone moment. Let's take a more in-depth look at how the Linx AirLok solution combines the strengths of previous approaches and adds entirely new benefits as well.