To the line, thus hastening the discharge and the return of the relay tongue to its insulated stop.
The Siemens polarized relay, shown in fig.
When the relay is operated it connects a bell between one of the wires of the circuit and earth, while the bell itself is arranged to respond to current pulsations in one direction only.
The coils of the electromagnets are differentially wound with silk-covered wire, 4 mils (= 004 inch) in diameter, to a total resistance of 400 ohms. This differential winding enables the instrument to be used for " duplex " working, but the connexions of the wires to the terminal screws are such that the relay can be used for ordinary single working.