Abstract: When communication utilizing a first protocol that is normally employed in a network wherein communication can be performed by a plurality of protocols fails, the cause of failure is examined by communication using a second protocol, and communication is recommenced utilizing the first protocol by automatically performing repair. Consequently, communication using the first protocol can be recommenced without interruption of communication, without requiring a correction operation by manual action by the operator.

Abstract: A computer communicates with a printer. The computer has a printer communication controller for controlling one-way and two-way modes for printing. The printer has a printing controller for controlling the one-way and two-way modes. The computer sends a switching signal to the printer through a switching signal line, to switch the printer from the one-way mode to the two-way mode. The switching signal is a signal in response to which the printer can return a response to the computer through a reception channel even if the printer is offline. Upon receiving the switching signal, the printer returns a response to the computer and switches to a pseudo two-way mode that is a temporary online state. If the computer sends a printing start command thereafter to the printer, the printer switches from the pseudo two-way mode to the two-way mode. This arrangement easily switches the one-way and two-way modes from one to another.

Abstract: In facsimile terminal equipment, ID numbers to be rejected are stored in advance and, when a received ID number is included in the stored ID numbers, a command to disconnect facsimile communication is transmitted to a transmitting facsimile terminal. Unnecessary communication can thereby be rejected without removing the advantage of facsimile communication that an image can be received from any unspecified subscriber.