# Lionel Sound Activation Button



## limitwheel (Jan 8, 2011)

I have a Lionel Southern Pacific Daylight loco with tender whistle/bell sounds. It came with a sound activation a button. My old ZW transformer will activate the whistle sounds only. I guess the activation button is needed for the bell sounds. 
What exactly does this button do electrically speaking? 
If my old ZW gives it a DC pulse when activating the whistle, does the sound activation button reverse the polarity of the DC pulse to make the bell sound?


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## gunrunnerjohn (Nov 10, 2010)

The Whistle adds a negative DC bias to the center rail, the sound activation button can be connected to add a positive DC bias to the center rail, that will activate the bell.


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## Leonard62 (Jan 7, 2011)

limitwheel said:


> I have a Lionel Southern Pacific Daylight loco with tender whistle/bell sounds. It came with a sound activation a button. My old ZW transformer will activate the whistle sounds only. I guess the activation button is needed for the bell sounds.
> What exactly does this button do electrically speaking?
> If my old ZW gives it a DC pulse when activating the whistle, does the sound activation button reverse the polarity of the DC pulse to make the bell sound?


I ran the activation button when I was using my ZW transformer as well. It works quite well. 

Len


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## limitwheel (Jan 8, 2011)

My assumption was right about the -DC causing the bell to ring in the tender. 
I opened up the Lionel sound activation button and saw 6 barrel diodes. My question is why are there so many diodes when 1 would do the trick?


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## gunrunnerjohn (Nov 10, 2010)

They are dropping the A/C voltage for electronic horns. Someone posted a diagram of the circuit here and the details of construction.


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## T-Man (May 16, 2008)

Each diode drops the voltage by .7 volts.
The DC is used to activate the relay or board.
One Diode is not bypassed since two buttons can be used to prevent a short.


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## knotscott (Feb 16, 2011)

I was researching exactly the same question on Google, and stumbled onto this discussion....just wanted to say thanks! :thumbsup:


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