Control system and control method

A control method fora control system which comprises a plurality of units,

• wherein the plurality of units includes
• a first unit, and
• a second unit which is able to communicate with the first unit, and
• wherein the control method comprises:
• a step of the first unit requesting an input of a user account to an external device constituted to be able to communicate with the first unit upon reception of a request for access to the first unit from the external device and transmitting the user account directly to the second unit upon reception of the user account from the external device;
• a step of the second unit referring to registration information defining account information of registered users, determining whether or not the user account received by the second unit has been registered, and transmitting a token indicating permission of access directly to the first unit when it is determined that the user account received by the second unit has been registered;
• and
• a step of the first unit transmitting the token received from the second unit to the external device,
• wherein an access authority is associated with each user account defined in the account information,
• wherein the second unit refers to the account information upon reception of the user account from the external device, identifies the access authority associated with the user account, and further transmits the identified access authority to the first unit when the token is transmitted to the first unit, and
• wherein the first unit transmits information according to the access authority received from the second unit to the external device,
• wherein an operation mode of the control system includes a maintenance mode indicating that the control system is under maintenance, and
• wherein the first unit or the second unit rewrites the access authority of a kind set in advance as an access authority of another kind set in advance when the operation mode of the control system is the maintenance mode.