The stackable Productivity1000 micro-modular PLC system provides communication; user-friendly programming; integrated data storage; and a lineup of discrete, analog and specialty I/O modules in a super-compact size. The system can be expanded with as many as eight I/O modules for a total of 128 discrete I/O points or 48 analog I/O channels. Direct-current modules include higher-density 16- and 15-pt Vdc models and 8- and 16-pt Vac/Vdc input versions. The line also includes 8-pt 120-240 Vac I/O modules; RTD four-channel input; combination four-channel input, two-channel output; and 0-20 mA and 0-10 Vdc modules.