The ’HC147 and CD74HCT147 are high speed silicon-gate CMOS devices and are pin-compatible with low power Schottky TTL (LSTTL).

The ’HC147 and CD74HCT147 9-input priority encoders accept data from nine active LOW inputs (l₁ to l₉) and provide binary representation on the four active LOW inputs (Y0\ to Y3\). A priority is assigned to each input so that when two or more inputs are simultaneously active, the input with the highest priority is represented on the output, with input line l₉ having the highest priority.

These devices provide the 10-line to 4-line priority encoding function by use of the implied decimal "zero". The "zero" is encoded when all nine data inputs are HIGH, forcing all four outputs HIGH.