[Dave Moll]

I don't think it's related to where the capacitor is located. After all, the 700 series of telephones pre-dates the introduction of master sockets with capacitors in them - and ringers were connected in series to avoid bell-tinkle when dialling.

The thing that seems strange to me is that a changeover switch was introduced with the 700s (in contrast with the simple switch in earlier 'phones to make a loop) but the chageover contact was shorted out.