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julie_m · 28th Jul 2019, 9:14 am

Batteries in series opposing would have to be in very different states of charge for the buzzers to sound. Only the difference between the two voltages is available to push a current, and the resistance is the two buzzers in series. The resulting current is unlikely to be enough to pull in either of the armatures enough to break the circuit, so the buzzers will stay silent until eventually the states of charge have equalised.

It's not even certain this configuration is actually used (but it would be a good way to minimise the voltage drop across the handset during calling).

28th Jul 2019, 9:14 am	#12
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Vintage Arrow ( Toy? ) Telephones Batteries in series opposing would have to be in very different states of charge for the buzzers to sound. Only the difference between the two voltages is available to push a current, and the resistance is the two buzzers in series. The resulting current is unlikely to be enough to pull in either of the armatures enough to break the circuit, so the buzzers will stay silent until eventually the states of charge have equalised. It's not even certain this configuration is actually used (but it would be a good way to minimise the voltage drop across the handset during calling). __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.