In power distribution circuits the circuit breakers are commonly coordinated by the use of instantaneous/time overcurrent relays or solid-state controllers. This paper explains that these devices can be replaced by a microprocessor-based system that provides high efficiency and reliability of control and operation of the circuit breakers. The design of a system is presented that constitutes a stand-alone dedicated controller specifically built for a power system rather than a general-purpose control system. For the flexibility of operation a keyboard matrix and a 16-character LED display are used for the operator to monitor the circuit breakers and feed the time-current parameters for their selective operation.