The 1747-L20B SLC 500 Fixed Controller by Allen-Bradley is a 20 I/O point capacity controller with twelve 120V AC inputs and eight Triac outputs. It has an AC voltage range between 120 and 240V AC and offers an optional two-slot expansion Chassis. The 1747-L20B has a 50VA maximum apparent power requirement and provides a 120-240V AC fuse protection of 1.25A. The 1747-L20B has a 5-year life lithium battery assembly backed RAM with 2 weeks of capacitor length and it offers either the UltraViolet Programmable Read Only Memory (UVPROM) or Electrically Erasable Programmable Read Only Memory (EEPROM) backup option. It is not equipped with a high-speed counter. However, it is equipped with features that formerly were limited to large controllers. It can be mounted onto the back panel using the mounting tabs of the enclosure and either #12 or #10 screws.   

The 1747-L20B has a processor program scan time of 8 milliseconds per 1K and the load-dependent holdup time ranges from 20-700 milliseconds. Some of the controller’s standard statuses are displayed using the LED indicator, which displays RUN, CPU FAULT, and FORCED I/O status, and its circuit uses the 24 AWG wire size. The 1747-L20B has an operational temperature range of 0-60 0C at non-condensing 5-95% relative humidity and it is stored at -40-85 0C non-operational temperature. It has an operational shock withstand of 30G and a vibrational withstand of 2.5G at 10-500Hz. The 1747-L20B is UL-listed and CSA-certified and it has the NEMA ICS2-230 standard Noise Immunity. Avoid removing the protective insulation that covers the circuit board. The 1747- L20B has 0.27 watts per point and power supply loading stands at a minimum of 10.5 watts and a maximum of 15.0 watts. Programming is limited to a maximum of 1024 bytes of memory. It uses Belden 9463 cable for robust, durable and reliable performance in industrial environments.