Pflüger's Law.
A law of electro-therapeutics. It states that stimulation of a nerve is
only produced by successive appearance of the kathelectrotonic state,
and disappearance of the anelectrotonic state.
Phantom Wires.
The extra transmission circuits obtained in multiplex telegraph systems.
A single line arranged for four separate simultaneous transmissions by
quadruplex apparatus is said to establish three phantom wires.
Phase.
In wave motion, oscillating motion, simple harmonic motion, or similar
periodic phenomena, the interval of time passed from the time the moving
particle moved through the middle point of its course to the instant
when the phase is to be stated.
Pherope.
An apparatus for the electric transmission of pictures. (See Telephote.)
[Transcriber's note: Precursor of the contemporary Fax and scanner.]
Philosopher's Egg.
An ellipsoidal vessel mounted with its long axis vertical and with two
vertical electrodes, the upper one sliding, and arranged to be attached
to an air pump. A discharge through it when the air is exhausted takes
the general shape of an egg.
Phonautograph.
An apparatus for registering the vibrations of a stylus, which is
mounted on a diaphragm and is acted on by sound waves.
It is virtually a resonating chamber, over one of whose ends a parchment
diaphragm is stretched. To the centre of the parchment a needle or
stylus is attached. A cylinder covered with soot is rotated in contact
with the point of the stylus. As the chamber is spoken into the
diaphragm and stylus vibrate and the vibrations are marked on the
cylinder. It is of some electric interest in connection with telephony.
Phone.
Colloquial abbreviation for telephone.
Phonic Wheel.
A form of small motor of very simple construction. It consists of a
toothed wheel of soft iron. A bar electro-magnet is fixed with one pole
facing the teeth of the wheel. By a tuning fork make and break a
succession of impulses of rapid frequency and short duration are sent
through the magnet. The teeth act as armatures and are successively
attracted by the magnet. The regulated speed is one tooth for each
impulse, but it may rotate at one-half the speed, giving two teeth for
each impulse, or at certain other sub-multiples of its regular speed. It
is the invention of Paul Lecour.