The 74LS133 is a 4-bit TTL equivalent part in the 74LS family of logic chips. It is a programmable logic device (PLD) used to store and decode truth tables. It has four inputs, A, B, C and D, that can be set to zero or one. The chip then outputs four separate outputs, Z1, Z2, Z3 and Z4, as well as a Truth Table output that is determined by the input A through D. This PLD is used primarily used for decoding and switching one of several inputs to a single output, or vice versa.