Took a look at the electronics and schematic details - Wow! 48 outputs, 24 inputs, RS-232 interface or RS-485 4-wire interface! Impressive design for a lot of good reasons. If someone needs that many or more digital Input/Output channels, can’t beat it with a stick. PCB and programmed IC are about $60, a complete kit about $104, w/o power supply, case.
There are Digital I/O devices available pre-built with up to 16 channels of I/O and either RS232 or RS485 serial connections. The advantage of the RS485 connections is that each module has it’s own address, so many of the same module can share the same wire pairs. The number of modules is limited by loading, generally to 32, but that can be overcome with a repeater for another 31. B&B Electronics Mfr. Co. has a nice RS422/485 Appication note on their website, www.bb-elec.com on the sidebar of the Technical Library, Support page.
They also have Digital I/O modules that can handle 16 channels of input or output, a bit of additional circuitry is needed to sink more current or handle relays. The 232SDD16 or 485SDD16 handles 16 channels, a driver module, the DBM16 plugs into that to provide pull-up or current sink drive for LEDs or relays. They specialize in RS232 to RS485/RS422 converters, so if someone doesn’t want to build everything, there are pre-built converters. I’ve been trying to think of what to do with 16 channels of input and/or output. Many industrial uses are much more limiting. Control is simple in Visual Basic or Quick Basic. There are relay modules available as well.
The electronics is not real complicated, but some knowledge is required to avoid overloading outputs, overvoltage on inputs. One thing I thought was cool about the MR SMINI is the built-in support for oscillating the outputs for yellow.
I’m looking forward to the rest of the article, more on sensor circuits. I missed the others, they were before I got back into trains, have only a few back issues with parts of articles.