The programmable logic controller (PLC) is a dedicated small computer that is mainly used in industries or other fields related to control systems.

Modern PLCs are powerful, high-performance devices that are protected against high levels of electrostatic discharge (ESD), large transient voltage fluctuations, electromagnetic interference (EMI), and are specially designed to operate in harsh industrial conditions. In most cases, these devices support many interfaces (RS485, Ethernet, CAN, LVDC. etc.) and communication protocols (Modbus, Profibus, CANopen, EtherCAT, DeviceNet, EtherNet I/P, etc.). PLCs are no longer limited to one programming language. They can be programmed in one of five languages - Function Block Diagram (FBD), Instruction List (IL), Ladder Diagram (LD), Sequential Flow Chart (SFC) and Structured Text (ST) - which correspond to the worldwide valid standards for programming languages of programmable logic controllers IEC 61131. Some PLC programming environments allow developers to flexibly combine different programming languages in a single CPU, e.g. using CODESYS V3.5. In addition to the support of many data types, extensive libraries, visualization elements, CODESYS can also implement its own protocols and create object-oriented control programs. Thanks to an extensive development environment and large memory capacity, complex and large process control projects for almost all industrial purposes can be implemented with one PLC.

Such high performance is not necessary if efficiency has a higher priority. Because of this, many manufacturers produce different simplified devices dubbing them "Programmable Logic Relay" (PLR), "Compact PLC", "Mini PLC", "Smart Relay", Small Controller", etc. These devices are typically non-modular and have less storage capacity, fewer interfaces/protocols and fewer I/O points, making them more compact. These simplifications lead to a reduction in device costs. They are at least two times cheaper compared to PLCs. Another advantage of the PLRs is that they are easier to program because they are usually delivered with an intuitive and user-friendly programming environment, saving time and money.

The akYtec GmbH does not remain on the sidelines of this trend and offers PLR-like devices as well – Programmable Relays of the PR1XX series, and a more sophisticated device of this kind – PR200. They are all equipped with a real-time-clock and can be expanded with I/O-modules. The easy-to-use and free "akYtec ALP" software tool can be used to create simple and effective solutions for industrial needs such as pump control, lighting, HVAC, home automation, and other simple automation tasks without complicated and expensive PLCs.