Gas compressor

An apparatus comprising:

• a communication interface that is communicable with an external gas compressor;
• an input and output interface;
• and
• a control unit that communicates with the external gas compressor via the communication interface,
• wherein based on information input from the input and output interface, the control unit sets, via the communication interface, a host gas compressor as a master gas compressor that performs compressor number control on the external gas compressor as a slave gas compressor, or sets, via the communication interface, the host gas compressor as a slave gas compressor on which the compressor number control is performed by the external gas compressor as a master gas compressor,
• in a case where the host gas compressor is set as the master gas compressor, when one cycle of communication with N slave gas compressors as the external gas compressors in N communication sets is defined as a total compressor number communication cycle, in an initial total compressor number communication cycle, in first to Nth communication sets, the control unit transmits a first response request to each of first to Nth slave gas compressors, and when the control unit receives a response from the slave gas compressors, the control unit determines that communication connection with the slave gas compressors has succeeded, and when the control unit receives no response from the slave gas compressors, the control unit determines that communication connection with the slave gas compressors has failed, and
• in second and following total compressor number communication cycles, the control unit transmits a second response request to the slave gas compressors, with which the communication connection has succeeded, in each of the communication sets, and transmits the first response request to the slave gas compressors, with which the communication connection has failed.