Abstract: A key telephone system has an oscillation preventing circuit comprising a termination impedance element, said circuit is a switching element and connected between the ground and another circuit which includes an impedance compensating circuit, therein. The switching element is turned ON upon oscillation of the impedance compensating circuit due to any remarkable impedance fluctuation in the signal transmission line, thereby effectively suppressing such oscillation of the impedance compensating circuit to maintain a favorable transmission efficiency.

Abstract: A data transmission system between a main CPU and a plurality of sub-CPU's includes a data bus connected between them, a CPU select line for transmitting a CPU select signal from the main CPU to the sub-CPU's, a latch circuit for providing a wait signal to the main CPU upon write or read in the main CPU with respect to the sub-CPU's and a wait clear line connected between the respective CPU's to provide to the latch circuit a wait clear signal upon completion of input and output of the sub-CPU to release the waited state of the main CPU, the transmission system being thereby simplified to reduce installation space and wiring labor.

Abstract: A telephone exchange equipment system for enabling transmission of a speech message from a fresh calling party to another busy party without interruption of the connection for the original conversation. Each of the telephone sets are connected to the exchange equipment through a four-wire cable comprising a transmitting line and a receiving line. The exchange equipment is provided with a mixer having two input terminals and an output terminal.

Abstract: A bus-method communication network has a number of stations with assigned station numbers. An exclusive right or priority of transmission is transferred from a first station to a second station by transmission of an abort signal including synchronization information and a first address assigned to the first station. In each station, a waiting time is calculated from a first station number in the detected abort signal and the station number assigned to the receiving station. When the associated waiting time elapses, another station seizes priority as a second station and transmits a paging signal having a destination address following communication data. Each station is prevented from seizing transmission priority in response to reception of the paging signal, and the station having the destination address decodes the communication data. The second station thereafter transmits the abort signal.

Abstract: An operator panel for a data input unit has a printed circuit board on which key switches corresponding to a number of commodities are arrayed. A flexible sheet is bonded over the keytops of the key switches. Photographs depicting the external appearance and shape of the commodities, or sketches showing the characteristics of the commodities, are printed on the flexible sheet at positions overlying respective ones of the keytops. The sheet has enough flexibility to enable operation of the key switches without hindrance. To input data relating to a desired commodity, an operator finds the photograph or sketch of the commodity on the flexible sheet and presses this portion of the sheet, thereby pressing the underlying commodity key switch to effect the entry of the data.

Abstract: A circuit for sending out a ringing signal of a high voltage and a low frequency to a telephone set through a telephone line repeatedly with a predetermined time interval. In order to omit use of a high power oscillator and relays, a D.C. power supply of a high voltage is operatively connected to the telephone line through phototransistors of photocouplers being driven by a pulse signal having a low voltage and the low frequency under control of pulses occurring at the predetermined time intervals so that the ringing signal is sent out to the telephone set repeatedly with the predetermined time interval.

Abstract: A simple data input apparatus is equipped with a magnetic card reader and uses an input guide sheet. The input guide sheet has such input items as service number, commodity number, quantity and unit price printed thereon and includes a magnetic strip storing the order in which these items are to be indicated. The simple data input apparatus is provided with an input guide section on which a plurality of indicating lamps are arranged. The data stored on the magnetic strip of the input guide sheet are read by the magnetic card reader and written into a RAM provided inside the apparatus. The input guide sheet is then placed on the input guide section and the indicating lamps light sequentially in accordance with the input item indication order written into the RAM from the magnetic strip.

Abstract: In a receiver receiving a time-division multiplex signal of a plurality of channels with each channel signal having a start signal part, an address signal part, an information signal part, and a blank interval arranged in this order, a channel detecting circuit for detecting the channel signal assigned to the receiver is provided with a blank interval detecting circuit in addition to an address detecting circuit for detecting the address signal part representing the address assigned to the receiver, in order to avoid an erroneous detection of the address detection circuit at a start condition of the receiver. Application of the multiplex signal to the address detecting circuit is prevented until the blank interval detection circuit initially detects one blank interval of the multiplex signal.

Abstract: An extension ringing arrangement for a key telephone system wherein a plurality of key telephone sets are connected respectively through associated plurality of channel units to main equipment including a main CPU. The channel units as well as an interface unit, including a sub-CPU interconnected to the main CPU are connected in parallel to the main equipment. The interface unit is of the type used for interconnecting individual line telephone sets to the key telephone system, whereby a ringing of a selected one of the key telephone sets from a calling party is made possible, with a simple arrangement effectively utilizing existing components of the key telephone system.