They achieve the high speed operation similar to equivalent LSTTL while maintaining the CMOS low power dissipation. The 74HC240A is an inverting 3-state buffer having two active-low output enables. The TC74HC241A and TC74HC244A are non-inverting 3-state buffers that differ only in that the 241A has one active-high and one active-low output enable, and the 244A has two active-low output enables. These devices are designed to be used with 3-state memory address drivers, etc.