Inverting buffer for 5 V bus isolation
Each of the two elements handles four bits, with output drive rated at 32 mA source and 64 mA sink — enough to drive a heavily loaded backplane or a bank of LED indicators without external buffers.
The 32 mA source / 64 mA sink current rating is the headline selection parameter. On a 5 V backplane with multiple loads, the 64 mA sink handles the low-level current from a dozen TTL inputs or a long trace's capacitive discharge. If your system is mixed-voltage, you need a level-translating buffer like the 74LVTH series.