When Märklin introduced the Märklin Digital system in 1984, it supported 80 addresses, which if is an odd number, well not literally, but still, this is not a power of two or even close. Later they introduced the Märklin Delta system, which only supports four addresses (that makes sense), with addresses 24, 60, 72 and 78. All these number are even, but the values do not match the pattern computer scientists have learned to recognise. What is going on?

It turns out the Märklin digital system uses a base three encoding, i.e. the wire protocol has three symbols, 0, 1, and open. Addresses are encoded on 4 symbols, so there are 3⁴ = 81 possible addresses, with one reserved for the controller. The table for delta addresses now look like that (the Delta system did not use addresses, but locomotive type icons):

Basically, the delta addresses are the four possibilities using only the 0 and 2 symbols, with a constant 0 at the start and no sequence of three zeroes.