The M224 (formerly Agilent E2291A) provides 16 isolated open-collector digital outputs in four groups of four. Each group of four requires its own external +5V supply.
The M223 (formerly Agilent E2290A) provides 16 data/actuator lines. These data lines offer TTL compatible inputs and open drain outputs up to 30 volts.
The PX451S is a 16 or 32 channel digital input module that samples and selectively stores up to 32 bits of digital data along with a 31-bit time stamp at a rate up to 5MHz.