IRE (unit)
From Infogalactic: the planetary knowledge core
An IRE is a unit used in the measurement of composite video signals. Its name is derived from the initials of the Institute of Radio Engineers.[1]
A value of 100 IRE was originally defined to be the range from black to white in a video signal. A value of 0 IRE corresponds to the voltage value of the signal during the blanking period. The sync pulse is normally 40 IRE below this 0 IRE value, so the total range covered from peak to trough of an all white signal would be 140 IRE.
The reason IRE is a relative measurement (percent) is because a video signal may be any amplitude. This unit is used in the ITU-R BT.470 which defines PAL, NTSC and SECAM.[2]
