Method to alert a phone operator by magnetic means of an incoming call

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG.
1, a magnetostrictive generator 10 constructed in accordance with a broad aspect of the invention includes an autotransformer 12 having a primary winding 14 connected in series with a secondary winding 16, the both windings being wound around a common core (not shown) formed of a material exhibiting high magnetostrictive properties.
A tap 18 between the windings 14 and 16 is connected to a battery 20.
A capacitor 22 is connected in parallel with the primary and secondary windings 14, 16 of the transformer 12.
A transistor 24 is connected in series with the primary winding 12 and controlled from an input 26 through an isolating capacitor 28.
A storage capacitor 30 and a limiting resistor 32 connected in series are placed in parallel to the transformer 12 and a controlling junction of the transistor 24.
In operation, briefly, when an electric signal appears at the input 26, the transistor 24 opens and a current begins to flow through the primary winding 14 of the transformer 12.
Since the winding 12 and 14 are wound on the common core, the voltage developed across the primary winding 14 produces in turn a voltage across the secondary winding 16, and the combination of the voltages across the windings 14, 16 is applied to charge the commutating capacitor 22.
During the most of the time the commutating capacitor 22 is being charged, the core of transformer 12 is in an nonsaturated state so it has a relatively high inductance and, therefore, the current flowing in the loop comprising the primary and secondary windings 14, 16 of the transformer 12 and the communicating capacitor 22 is relatively low.
As the charge upon the commutating capacitor 22 increases to a sizable value, the core of the transformer 12 saturates, and the inductance decreases to a lower value at which it can no longer support the high voltage across the capacitor 22.
Discharge of the energy stored in the commutating capacitor 22 through windings 14, 16 causes the current flowing through both the windings 14, 16 to substantially increase that drives the core further into saturation