GPS Systems require altitude data to perform certain correction, including missing satellite information. Also, to maintain 3-D accuracy, GPS units cannot receive gray code output which was standard on old encoders. They are designed to accept serial data. Thus, a device wad required to convert 10-wire gray code data from the altitude encoder to an acceptable serial format. (That is, until Shadin Avionics designed the fine Altitude Encoder 8800X with built-in serial port! See Falcon Altitude Encoder for more details.
The Shadin Avionics serializer line of products take 10 wire gray code from your existing Mode C encoder and converts that into an RS-232 format. The converter also has the capability of driving 2 independent altitude devices: at the same time your GPS/Loran, and the Shadin Avionics AMS-2000!
The low resolution serializers are a family of Shadin Avionics products which take gray code as an input and output serial data. They are referred to as 9000 series products.
They are referred to as \"low resolution\" because the gray code has a resolution of 100 feet increments. So the altitude which they transmit on their serial ports always has 0\'s in the 1\'s and 10\'s places.