Y amplifier Same as vertical amplifier.

Y-cut crystal A slice of quartz crystal cut at right angles to a Y axis and parallel to the optic axis. A quartz crystal has the shape of a hexagonal prism and the Y axes (mechanical axes) pass through the centre and the midpoints of opposite sides of the hexagon as shown in Figure Y.1. The line through O perpendicular to the plane of the paper is the optic axis of the crystal. The shaded area on the diagram represents a Y cut. Such slices are used to control the frequency of oscillators, e.g. those used to generate the carrier frequency of radio transmitters but a disadvantage is that the natural resonance frequency of the slice (determined by its thickness) is temperature dependent so that, for high frequency stability, the temperature of the slice must be controlled within narrow limits.

yoke A piece of magnetic material used to complete a magnetic circuit. The yoke is not itself surrounded by windings but it often acts as a mechanical support for windings as in the deflection coil assembly of a TV picture tube.

y parameters Of a transistor, a method of expressing the electrical characteristics in which the input and output currents are given in terms of the input and output voltages. The two fundamental equations are:

where y_i is the input admittance (for short-circuited output terminals); y_o is the output admittance (for short-circuited input terminals); y_i is the reverse transfer admittance and y_f is the forward transfer admittance.

Y plates See deflector plates.

Y signal Same as luminance signal.