End of 2001 märklin offered their second Premium Digital Starter Set, number 29855, that contains a class 18.4 steam loco, and a class E 40 electric loco. Both locos have sound modules built in.
In its original form this sound module produces two different horn sounds. They are triggered in an unusual way: The digital function f2 acts like a selector, and f3 starts the selected sound.
The sound board is separate from the decoder. It is made using modern advanced production technology. The printed circuit board is a 4-layer board, the outer layers are used for signal routing, the inner two layers are a ground layer and a positive voltage (that of the sound IC) layer. This allows for good shielding and high component density. SMD components are used throughout, with resistor and capacitor sizes down to 0603. That is very tiny. The board is populated on both sides, but the SMD components are not glued to the board. Three components have an unusual marking: R10, R14, and R24 are marked "310" or "OIC", but they are very likely 10k resistors.
The size of the sound board is: 58 mm × 22 mm × 4 mm.
The decoder is clipped on the back of the sound board into a plastic holder. It is identical to the 60902, but apart from f1 and f2 it has an additional third function output f3. Function f1 is unused and available. Functions f2 and f3 are connected to the sound board.
Here is a photo of the sound board's "component side":
And a photo of the "solder side":
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last update: 2002-05-19
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