Summary: Trinary is a method of representing digital signals using three states, instead of the two used for Binary.
Motorola Trinary is an old data format the came from the Marklin Digital system, based on Motorola parts. The Marklin system was developed by under contract by outside firms including Lenz, whose designs were also used for the Arnold Digital system.
The main reason for using Trinary instead of Binary was for the purpose of reducing component count and costs.
Trinary refers to the digital logic being able to represent three states, instead of the two states found in binary logic. This is done using 2 bits that can represent three states, On/Off and Open. On and Off would be the equivalent of the One and Zero states of binary logic. The Open could be interpreted to have a value of 2.
The Marklin Digital brand represents the majority of command control systems used in Germany, but it's not as common elsewhere, and it's not compatible with the NMRA DCC Standard. It actually used different frequencies to transmit digital information to mobile or stationary decoders. Other manufacturers do offer DCC decoders and command stations which can handle this format.
The Motorola Trinary format was originally deployed for industrial control purposes. In 1985 it was used with the Marklin Digital system. It is not suited to two-rail operation, as it is polarity sensitive. So it was ideal for the Marklin three-rail AC trains.
There were two formats of signalling used. For accessory decoders, the high pulse was 13 mS (milliseconds) long. The low pulse was 91 mS. The voltages ranged from +18 to -18V.
For locomotives, the signals were twice as long, or 26mS and 182mS.
Transmitting data was unique as well. A short High, followed by a long Low, then another short HIGH long Low equalled zero. Inverting that into a pair of long High/short Lows was interpreted as a one.
Where a L or H equals 1 period:
- Binary 1 = HLLLLLLHLLLLLL
- Binary 0 = LHHHHHHLHHHHHH
A third character, X, was formed by a long High, short Low, short High, long Low. Later on another character would appear, "Y", in the Modified Motorola format, formed by short High, long Low, long High and a short Low.
- Binary X = HHHHHHLHLLLLLL
- Binary Y = HLLLLLLHHHHHHL
The system is polarity sensitive, high is the positive voltage, low is negative. If inverted in polarity, many older decoders would not understand the signals. Later decoders could detect the incorrect polarity and deal with it.