Selectrix
Selectrix is a digital control system for model railways that can be used for driving, switching, reporting and controlling.
development
The technology used at Selectrix (SX) was developed by Doehler & Haass (D&H). Selectrix is a registered trademark of the Trix company in Nuremberg (since 1997 Märklin ), but independent suppliers have also been licensed by Doehler & Haass. The vehicle decoders are almost all manufactured by Doehler & Haass, the multi-protocol decoders for DCC / Selectrix operation from Uhlenbrock, and the Selectrix decoder from CT Elektronik is an in-house development.
The modern decoders for Selectrix / DCC operation in model railway vehicles from the company Döhler and Haass can be updated, offer several function outputs, function mapping, etc. Digital accessories for controlling the model railway are now in so-called small series due to a large remaining market niche still developed and sold by the company strengz among others. The development of large series projects and the extensive sales of SX products in large numbers was discontinued by Trix's parent company, Märklin, after the SX project was over.
protocol
Selectrix in version 1 uses a protocol according to the documentation NEM 680 and NEM 681 between the control center and all decoders. This means that there is an identical signal both on the track and on the bus cables between the devices. The communication between these is - unlike DCC - also standardized.
The addressing is solved very differently compared to the DCC system. See NEM 681. A base address is followed by 7 data packets (e.g. 7 locomotives), followed by the next address and its data packets. The data for all system addresses are sent or repeated on the bus 13 times per second. Changes to speed or control commands are guaranteed 1/13 of a second after being triggered by the receiver. The Selectrix bus is therefore real-time capable. In contrast to this, DCC and Märklins mfx are packet-oriented protocols with a speed that depends on the activity on the bus.
Furthermore, the number of additional functions that can be addressed under one address is significantly smaller than, for example, with modern DCC decoders (a good 100 compared to around 10,000). The options for setting the decoder with the Selectrix protocol depend on the type of decoder. Depending on the system, the decoders have 31 (external) speed steps, internally either 31 or 128. There are 112 system addresses on each Selectrix bus. These can be used at the same time, for example for 112 locomotives or 8 × 112 turnouts or track occupancy detectors - or corresponding mixed forms. Some control centers offer several Selectrix buses in order to increase the address space.
Opinions differ on the advantages and disadvantages of both solutions, the Selectrix supporters emphasize the constant speed (load independence) of their solution, the extensive range of decoders for many tasks (e.g. light signal decoders, turntable control) and the compatibility between all providers, the users other systems criticize the limited functionality of the Selectrix protocol and the limited address range.
Application area
For historical reasons, Selectrix is mainly used for the small tracks N and Z, as well as partly in TT, as these decoders had the smallest dimensions for a long time. Most widespread, however, is the DCC system based on a development by the Lenz company , as well as the Märklin-Motorola digital system or Märklin Systems from Märklin in the H0 AC range . Outside of Europe there is practically only DCC.