0 a device made from a piece of iron that becomes magnetic when a changing current is passed through the wire that goes around it -- 電磁鐵；電磁體
This "musical telegraph" used steel reeds with oscillations created by electromagnets transmitted over a telegraphy line.
Eventually, single-channel gave way to multi channel devices (at significantly higher cost) with various audio tones driving electromagnets affecting tuned resonant reeds for channel selection.
The central controller system vibrated the electromagnet like an audio-speaker voice coil.
With this configuration the armature is through-bolted through the door and oriented to mate with the face of the electromagnet.
I do not know whether they are using electromagnets or something like that, but they appear to hoover the sea.
Voltages induced in the receivers by three fixed electromagnets situated around the subject's head were used to determine location of the receivers in the midsagittal plane.
Consider an electromagnetic field surrounding an electromagnet.
The electromagnet's current links the display of time on the clockface with the measurement device in the chronoscope.
