OSCILLATION TRANSFORMER.--See _Transformer, Oscillation._

OSCILLATIONS, ELECTRIC.--A current of high frequency that surges through an open or a closed circuit. (1) Electric oscillations may be set up by a spark gap, electric arc or a vacuum tube, when they have not only a high frequency but a high potential, or voltage. (2) When electric waves impinge on an aerial wire they are transformed into electric oscillations of a frequency equal to those which emitted the waves, but since a very small amount of energy is received their potential or voltage is likewise very small.

Sustained.--Oscillations in which the damping factor is small.

Damped.--Oscillations in which the damping factor is large.

Free.--When a condenser discharges through an oscillation circuit, where there is no outside electromotive force acting on it, the oscillations are said to be _free._

Forced.--Oscillations that are made to surge in a circuit whose natural period is different from that of the oscillations set up in it.

OSCILLATION TRANSFORMER.--See _Transformer._

OSCILLATION VALVE.--See _Vacuum Tube._

OSCILLATOR TUBE.--A vacuum tube which is used to produce electric oscillations.

OVER MODULATION.--See _Blub Blub._

PANCAKE OSCILLATION TRANSFORMER.--Disk-shaped coils that are used for receiving tuning inductances.

PERMEABILITY, MAGNETIC.--The degree to which a substance can be magnetized. Iron has a greater magnetic permeability than air.

PHASE.--A characteristic aspect or appearance that takes place at the same point or part of a cycle.

PICK-UP CIRCUITS.--See _Circuits, Stand-by._

PLATE CIRCUIT REACTOR.--See _Reactor, Plate Circuit._

PLATE CURRENT.--See _Current, Plate._

PLATE MODULATION.--See _Modulation, Plate._

PLATE VOLTAGE.--See _Foliage, Plate._

POLES, BATTERY.--The positive and negative terminals of the elements of a battery. On a storage battery these poles are marked + and - respectively.

POLES, MAGNETIC.--The ends of a magnet.

POSITIVE ELECTRICITY.--See _Electricity, Positive._

POTENTIAL DIFFERENCE.--The electric pressure between two charged conductors or surfaces.

POTENTIOMETER.--A variable resistance used for subdividing the voltage of a current. A _voltage divider._

POWER TRANSFORMER.--See _Transformer, Power._

POWER TUBE.--See _Generator Tube._

PRIMARY BATTERY.--See _Battery, Primary._

PREVENTION, KICK-BACK.--A choke coil placed in the power circuit to prevent the high frequency currents from getting into the transformer and breaking down the insulation.

Q S T.--An abbreviation used in wireless communication for (1) the question "Have you received the general call?" and (2) the notice, "General call to all stations."

QUENCHED GAP.--See _Gap, Quenched._

RADIATION.--The emission, or throwing off, of electric waves by an aerial wire system.

RADIO AMMETER.--See _Ammeter, Hot Wire._

RADIO FREQUENCY.--See _Frequency, Radio._

RADIO FREQUENCY AMPLIFICATION.--See _Amplification, Radio Frequency._

RADIO FREQUENCY CURRENT.--See _Current, Radio Frequency._

RADIO INSPECTOR.--See _Inspector, Radio_.

RADIOTRON.--The trade name of vacuum tube detectors, amplifiers, oscillators and modulators made by the _Radio Corporation of America_.

RADIO WAVES.--See _Waves, Radio_.

REACTANCE.--When a circuit has inductance and the current changes in value, it is opposed by the voltage induced by the variation of the current.

REACTANCE, CAPACITY.--The capacity reactance is the opposition offered to a current by a capacity. It is measured as a resistance, that is, in _ohms_.

RECEIVING TUNING COILS.--See _Coils, Inductance_.

RECEIVER, LOUD SPEAKING.--See _Loud Speakers_.

RECEIVER, WATCH CASE.--A compact telephone receiver used for wireless reception.

REACTANCE, INDUCTIVE.--The inductive reactance is the opposition offered to the current by an inductance coil. It is measured as a resistance, that is, in _ohms_.

REACTOR, FILTER.--A reactance coil for smoothing out the pulsating direct currents as they come from the rectifier.

REACTOR, PLATE CIRCUIT.--A reactance coil used in the plate circuit of a wireless telephone to keep the direct current supply at a constant voltage.

RECEIVER.--(1) A telephone receiver. (2) An apparatus for receiving signals, speech or music. (3) Better called a _receptor_ to distinguish it from a telephone receiver.

RECTIFIER.--(1) An apparatus for changing alternating current into pulsating direct current. (2) Specifically in wireless (_a_) a crystal or vacuum tube detector, and (_b_) a two-electrode vacuum tube used for changing commercial alternating current into direct current for wireless telephony.

REGENERATIVE AMPLIFICATION.--See _Amplification, Regenerative_.

RECEPTOR.--A receiving set.

RECEPTOR, AUTODYNE.--A receptor that has a regenerative circuit and the same tube is used as a detector and as a generator of local oscillations.