2 x SN74LS47 DIP16 through hole are Low Power Schottky BCD to 7-Segment Decoder/Drivers consisting of NAND gates, input buffers and seven AND-OR-INVERT gates.
They offer active LOW, high sink current outputs for driving indicators directly.
Seven NAND gates and one driver are connected in pairs to make BCD data and its complement available to the seven decoding AND-OR-INVERT gates.
The circuits accept 4-bit binary-coded-decimal (BCD) and, depending on the state of the auxiliary inputs, decodes this data to drive a 7-segment display indicator.
Output configurations of the SN74LS47 are designed to withstand the relatively high voltages required for 7-segment indicators.