Remote 8 Bit I/O Expander for I2C Bus with Interrupt, 100kHz, 2.5V, 6V, SOIC - 

The PCF8574T/3,518 is a 8-bit remote I/O Expander for I²C-bus with interrupt. It provides general-purpose remote I/O expansion via the two-wire bidirectional I²C-bus (serial clock (SCL), serial data (SDA)). The devices consist of eight quasi-bidirectional ports, 100KHz I²C-bus interface, three hardware address inputs and interrupt output operating between 2.5 and 6V. The quasi-bidirectional port can be independently assigned as an input to monitor interrupt status or keypads or as an output to activate indicator devices such as LEDs. The low current consumption of 2.5μA (typical, static) is great for mobile applications and the latched output ports directly drive LEDs.