Abstract: When the person in charge of reception registers visit information of a visitor beforehand, a visitor identification code is issued, and the visitor acquires the visitor identification code on a mobile terminal of the visitor. The visitor holds the visitor identification code displayed on the mobile terminal of the visitor over a reader that cooperates with a reception telephone to cause the reader to read the visitor identification code. The reception telephone automatically makes a call to a communication device of the person in charge of reception, the person in charge of reception responds on the communication device, and a call is established between the visitor and the person in charge of reception. The person in charge of reception confirms the visitor on a display unit that cooperates with the communication device from an image of the visitor imaged by a camera, and entry of the visitor is permitted.

Abstract: There is provided an interface circuit according to which a telephone or an intercom may be connected to a port of a main device including a telephone exchange function. The interface circuit includes a power supply circuit that supplies necessary power supply voltage according to the telephone or the intercom connected to the port, and a state detection circuit that detects, in a case where the telephone is connected to the port, whether the telephone is in an on-hook state or in an off-hook state, based on the value of an input impedance of the telephone, and that detects, in a case where the intercom is connected to the port, whether the intercom is in a standby state or in an activation button pressed state, based on a value of the input impedance of the intercom.

Abstract: There is provided an interface circuit according to which a telephone or an intercom may be connected to a port of a main device including a telephone exchange function. The interface circuit includes a power supply circuit that supplies necessary power supply voltage according to the telephone or the intercom connected to the port, and a state detection circuit that detects, in a case where the telephone is connected to the port, whether the telephone is in an on-hook state or in an off-hook state, based on the value of an input impedance of the telephone, and that detects, in a case where the intercom is connected to the port, whether the intercom is in a standby state or in an activation button pressed state, based on a value of the input impedance of the intercom.

Abstract: A small portable memory device has optical connectors except for those connecting with an external power source. The memory device incorporates a semiconductor memory and information such as address and data information are applied externally by means of light beams. The light signals applied to the device are converted into electrical signals by phototransistors and the address and data information applied externally, one bit at a time, are temporarily stored in a shift register incorporated in the device. When the received input attains a predetermined number of bits, the semiconductor memory is accessed to effect the writing or reading of data. When reading the data, electrical signals indicative of the data to be read are converted into light signals by a light-emitting diode and are delivered from the device in the form of light signal.