Lionel Bell and Whistle Controller
Now here is a shift in topic. And, yes, we are talking about Lionel model trains and, more specifically, how to activate the bell and whistle functions on both old and new locomotives (Not including the new digital control versions, e.g. TMCC).

Back in the olden days Lionel evolved a simple way to add a 'control function' to their train sets. Normally Lionel trains use AC power on the track  - 5 to 18 VAC.  In order to control an accessory (e.g. a whistle) they added a low voltage dc relay in the train. The contacts on this little relay then drove the accessory device (e.g. the whistle). Then they just added (activated by a switch) a low voltage dc offset to the normal ac power signal going to the track . The relay in the load was activated by the dc signal and the relays contacts activated the load.

As Lionel morphed into the digital world, they retained this same basic mechanism for activating simple functions such as the whistle and the bell. To get two functions to work, they simply used one polarity of dc offset for one function and the other polarity for the other function.

So how can we adapt an older transformer/train controller to work with one of the newer engines?  I'm working on that and I will have more to come.