Printing apparatus and USB equipment

A printing apparatus comprising:

• a first receptacle connector that couples a first external device that functions as a host and an arithmetic section to communicate with each other;
• a second receptacle connector that couples a second external device that functions as the host or a device and the arithmetic section to communicate with each other;
• and
• a USB controller that causes the arithmetic section to function as the device or the host based on a first electric signal input from the first external device via the first receptacle connector and a second electric signal input from the second external device via the second receptacle connector, wherein
• when the first external device and the first receptacle connector are coupled, the USB controller
• causes the arithmetic section to function not as the host but as the device when the second external device that functions as the device is coupled to the second receptacle connector,
• causes the arithmetic section to function as the device when the second external device that functions as the host is coupled to the second receptacle connector, and
• causes the arithmetic section to function as the device when the second external device is not coupled to the second receptacle connector.