In that case, I suppose you could theoretically probably get away with the 'crazy' approach (transformer secondaries and bells both in series, per BAS's diagram)
I have to say that I haven't come across one - but nor have I ever had a need to look for one. There are undoubtedly plenty of DP push switches out there, but most would probably not be suitable for use as a bell push.
PLAN B
I'm not totally clear as to what you mean. As I said, if you wanted to take that approach (the one he called 'crazy') you would have to wire it as per the diagram that BAS posted.
Sure, and that relates to the 'primary' (230V) sides of the transformers, which would obviously be wired (to the mains) 'in parallel'. To do as BAS was depicting, it's the 'secondary' (6V or whatever) sides of the transformers which would have to be wired in series (and 'the right way around' for it to work).
Clearly the ideal, but it's a choice that only the OP can make. ... and, of course, it was you who posted a diagram of a 'cobble' that. AFAICS, would actually work for the OP - and, had you not done that, we probably wouldn't even be discussing that possible approach
Will work provided both transformers have the same output voltage and are connected with the phases of their outputs as shown. Anti-phase
When the bell button is NOT pressed the voltages from the transformers cancel each other and no current can flow.
True - but as you say, that functioning is fairly crucially dependent on the voltage outputs of the two transformers being identical, which may not necessarily be the case. In contrast, putting both transformers (in-phase) and both bells all in series (per BAS's diagram) would not be critically-dependent on anything.Will work provided both transformers have the same output voltage and are connected with the phases of their outputs as shown. Anti-phase ... When the bell button is NOT pressed the voltages from the transformers cancel each other and no current can flow.
Because, as bernard said, the transformers are wired such that when the loop is closed, their voltages are 'opposite' and therefore cancel out - just as if you put two identical batteries in series with the positive of one connected to the positive of the other. However, for the reason I recently gave, I would not personally favour bernard's arrangement, since it relies on the voltages from the two transformers being identical for them to perfectly 'cancel' in the closed loop. 'Clever' though bernard's idea is, the system in BAS's diagram would IMO be more 'foolproof'.
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