The Märklin 72441 Digital brake module was introduced to give the model railroaders a possibility to smoothly decelerate locos equipped with the 6090-type decoder with "speed regulation" in front of signals. Normally the 6090-type of decoders come to an immediate stop when track power is lost due to the strong magnetic field of the motor stator (permanent magnet). The Märklin item is unfortunately rather expensive, and alternatives should be considered.
The digital brake module only works with 6090-type EMF decoders (EMF= ElectroMagnetic Feedback), and locos equipped with 6080, 6081 or Delta will stop immediately when they enter the "braking section".
The schematics and relay descriptions are provided by Huib Maaskant.
In case you should have any wonderings about relay types, read on.
The big difference between a bistable and monostable relay is that the first category uses two coils, just as an electrical turnout (which is in fact a bistable relay). The monostable relay uses only coil. The monostable relays are much cheaper than the bistable ones.
How does a bistable relay work?
How does a monostable relay work?
Both types have different uses. You can however make a bistable relay out of two monostable relays, which is a lot cheaper than using a Märklin relay, especially if you can get monostable relays at an electronics dump store near you. Most relays work with either 12 VDC or 24 V DC.
BTW. You can make a very low cost block
signaling system out of a monostable relay: