Description:

Lot of 4 Texas Instruments SN74LS42N (74LS42) TTL logic ICs, marked “MALAYSIA 9009BS”. The SN74LS42 is a BCD-to-decimal (1-of-10) decoder/demultiplexer used to convert a 4-bit BCD input into one of ten active outputs for driving indicator circuits, address/select lines, or simple control decoding in vintage and modern hobby builds. Through-hole PDIP package—great for breadboards, retro repairs, and educational logic projects.

Modern uses:

- BCD-to-10-line decoding for LED/relay/transistor driver stages (with pull-ups)

- Retro computer/arcade/industrial board repair using 74LS logic

- Address / chip-select decoding in 5V TTL projects

- Educational labs: combinational logic, decoding, and demux demonstrations

Compatibility note:

Open-collector outputs require pull-up resistors and are intended to sink current (not source). Verify pinout (PDIP-16), logic family (74LS TTL), and supply voltage (5V TTL) before substitution; 74HCT42/74LS42 may be usable in some 5V designs, but confirm output type, timing, and load/current requirements.