Ohms:
is a unit for measuring resistance or impedance of any electrical device.

Omni directional transmitter:
is a transmitter which sends the signal in all directions.

Optical Filter:
is a type of filter used in optics which selectively allows light of different frequencies to pass through.

Oscilloscope:
is a device which visually displays the wave form of any electrical signal on a screen. In CCTV, it is used trouble shooting and making adjustments of various components.