Full description

7442 BCD to decimal (1 of 10) decoder

The 7442 outputs are active-low which means they become low when selected but are high at other times. They can sink up to about 20mA.
The appropriate output becomes low in response to the BCD (binary coded decimal) input. For example an input of binary 0101 (=5) will make output Q5 low and all other outputs high.

The 7442 is a BCD (binary coded decimal) decoder intended for input values 0 to 9 (0000 to 1001 in binary). With inputs from 10 to 15 (1010 to 1111 in binary) all outputs are high.

Note that the 7442 can be used as a 1-of-8 decoder if input D is held low.