These octal bus transceivers are designed for asynchronous two-way communication between data buses. These devices transmit data from the A bus to the B bus or from the B bus to the A bus, depending on the level at the direction-control (DIR) input. The output-enable input can be used to disable the device so that the buses are effectively isolated. The -1 version of the SN74ALS645A is identical to the standard version, except that the recommended maximum IOL is increased to 48 mA. There is no -1 version of the SN54ALS645A. The SN54ALS645A and SN54AS645 are characterized for operation over the full military temperature range of -55°C to 125°C. The SN74ALS645A and SN74AS645 are characterized for operation from 0°C to 70°C.