![]() Here in the US most of the telephone manufacturing market was cornered by Western Electric. A Google of hand crank magneto brings up several old telephone company magnetos which are surprisingly inexpensive at about $30 USD on Ebay. Will a square wave work? My best guess would be yes but I haven't a clue. My read on how much current is less than 30 mA and my guess is an AC sine wave of at least 60 volts at 20 Hz will ring any old rotary phone. C'mon we have to remember Jenny the exchange operator in Lassie? ![]() C'mon we have to remember Lassie? The hand crank magneto sent a ring signal to the operator at the exchange. Early phones actually had a crank magneto which was pretty cool. The lines were called Tip and Ring, the two wires from the phone. So when all is said and done how to make the phone ring? Apply a ring signal to the phones lines. The 48 VDC was called the loop supply or something like that. Capacitors block DC and pass AC and the ring signal was AC on the 48 VDC component. Why the capacitor? The capacitor blocked the 48 VDC commonly called the DC component. 47 uF and some 1.0 uF and the capacitor value is not critical. The ringer we are interested in worked on about 60 to 105 VAC at 20 Hz and it was a sine wave. So we place eight batteries in series and we have the 48 volts. Early 6 volt lead acid batteries were common as used in early automotive systems. The telephone worked on 48 VDC (Volts Direct Current) and early exchange systems had huge banks of batteries. So how to make your phone ring like the old days? Before we even get into that and speaking only for US phones we need to understand a few things. ![]() I will say this, here in the US where I happen to be a standard rotary dial phone had a life expectancy of I would guess 100 years including getting knocked off the table a few dozen times. The evolution of the rotary dial phone with its ringer is a long history. This thread has served as a pretty cool trip in a time machine.
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