Iwasaki Tsushinki Kabushiki Kaisha

Akihiko Suzuki

Hikaru Takematsu

A key telephone system, in which at least one CO line, at least one intercomm. line and control lines are arranged between a key service unit and a plurality of key telephone sets. The key service unit is provided with a scanning circuit for generating multiplexed code units indicating the connection state of each channel of said CO line and said intercomm. line in a time-division manner to scan the key telephone sets. The key service unit further includes means for transmitting the code unit to each key telephone set through said control lines. Each of the key telephone sets includes a decoder for decoding the code units thus transmitted to obtain individual indication signals indicating the states of each channel.

Key telephone system

A telephone set scanning type key telephone system, in which a plurality of key telephone sets are connected in parallel, to a key service unit through control lines composed of a display information line, key information line, a terminal selecting line and a clock line. Each key telephone set comprises a display memory, a key memory, a terminal coincidence circuit and a gate. The terminal coincidence circuit collates a selecting code transmitted thereto from the key service unit through the terminal selecting line and applies clock pulses transmitted thereto from the key service unit through the clock line to the gate to drive the display memory and the key memory only when the selecting code is coincident with the terminal number. A driving signal transmitted in the serial configuration from the key service unit through the display information line is stored in the display memory to develope a display and, at the same time, the key information stored in the key memory is applied in the serial configuration to the key service unit through the key information line.

Growing community of inventors

Mitaka, Japan

Akihiko Suzuki