SN74LS126AN .

The SN74LS126AN is a quadruple Bus Buffer features 3-state outputs that, when enabled, has the low impedance characteristics of a TTL output with additional drive capability at high logic levels to permit driving heavily loaded bus lines without external pull-up resistors. When disabled, both output transistors are turned OFF, presenting a high-impedance state to the bus so the output will act neither as a significant load nor as a driver. The LS126A device outputs are disabled when G is low.