The Ericsson engine works as follows: the working gas that is cooled in the recuperator and in the first cooler is compressed in the first compressor. The compression rate at this stage is as low as in the Stirling engine. The temperature of the gas at the compressor output is slightly higher than the temperature at the compressor input. After the first compressor the gas flows to the cooler that decreases its temperature. After that gas flows to the second compressor, where its pressure and temperature increase, but the temperature is returned to its previous value in the third cooler. In principle many stages of compression and cooling may be used to obtain a quasi-isothermal process of compression with high compression rate. A similar process occurs at the expansion of the gas. The difference is that we use expanders instead of compressors and heaters instead of coolers.