VERTICAL
AMPLIFIER

LUMINOUS

~)
GUN

HV SUPPLY

LV SUPPLY

TO ALL CIRCUITS cal

PLATES
TRIGGER TIME BASE HORIZONTAL
CIRCUIT GENERATOR AMPLIFIER

Block Diagram of a General Purpose CRO

HORIZONTAL
DEFLECTION
PLATES

The electron gun produces a focused and accelerated electron beam. The electron gun consists of a
heater, a cathode, a grid, a pre-accelerating anode and an accelerating anode.

Electrons are emitted from indirectly heated cathode. A layer of barium and strontium oxide is
deposited on the end of the cathode to obtain high emission of electrons at moderate temperature. These
electrons pass through a small hole in the control grid. The control grid is usually a nickel cylinder,
with a centrally located hole, coaxial with CRT axis. The control grid controls the number of electrons
passing through it. The intensity of electron beam is thus controlled by. the grid.