The access part of the network is displayed in the below figure. In the figure, MRC transmitters can be connected to the secondary side of the HV/MV (high voltage/low voltage) transformer, HV/HV and HV/LV transformer. It is associated with the dimensions of the controlled area and the power of a signal source (in a range of hundreds of kVA). Operating frequencies are in the range of 217Hz - 1050Hz.
To transmit MRC signals in an electric power grid, it is necessary to have a relatively powerful low-frequency AC power source signal with the output of hundreds kVA. They are also known as frequency converters. First, frequency converters were created using electromechanical rotating machines. At present, however, the power sources for MRC are constructed as Static Frequency converters (SFK), implemented by using a thyristor power inverter. The sources are mostly connected to the network using so-called serial links.
The need to distinguish between a number of objects and necessity to enhance operation security led to the creation of modern types of command codes for MRC. A command code with serial expression of dual commands (see picture) includes a start pulse (S) and a security gap (SG). Furthermore, it is the address part (A, B), which enables creating the conditions to increase the number of a possible dual command (up to hundreds). The command part includes 16 commands.
The original purpose of MRC, which was to support the operation of electric power grids during their development, exhibited considerable growth in amount of potential applications that can be divided into three main application groups.