These devices contain four independent 2-input-NOR line drivers. They perform the Boolean function Y = A + B\ or Y = A\ · B\. The SN54128 is designed to drive 75 ohm lines. The SN74128 is designed to drive 50 ohm lines. The SN54128 is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74128 is characterized for operation from 0°C to 70°C.