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US 4,536,615 AGranted
Key telephone equipment and associated method
AssigneeNitsuko Corporation
InventorsNorio Kimijima, Yuzuru Kawazoe
Life of this patent
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AssigneeNitsuko Corporation
InventorsNorio Kimijima, Yuzuru Kawazoe
Estimating the term…
Telephone apparatus including a main unit and a plurality of loudspeaker type key telephone sets, in which a pair of office line call wires to be used solely for an office line call, a pair of audio signal wires to be used for calling and talking with a loudspeaker and a pair of data wires to be used for time-sharing transmission of control data extend from the main unit. The respective loudspeaker key telephone sets all connect in parallel to these three pairs of wires. A neutral potential point of the audio signal wire pair and a neutral potential point of the data wire pair are coupled, on the main unit side, to a D.C. power supply via a D.C. network and to loudspeaker drive systems connected to the audio signal wire pair via an A.C. network. The neutral potential points on the button-switch telephone set side connect to a D.C. constant voltage circuit in each telephone set via a D.C. network and to a talking network in the telephone set via a transfer switch. Thereby the connecting path employing the audio signal wire pair as one conductor and the data wire pair as the other conductor can be used for supplying D.C. electric power to the respective telephone sets and for effecting an extension line call whereby the number of wires connecting the respective telephone sets to the main unit can be minimized to six.
Telephone apparatus comprising:
Telephone equipment adapted for connection to an external office line and an external A.C. power supply, said equipment comprising
A method of connecting a main unit of telephone equipment to a plurality of telephone sets for connection of the telephone sets to an external office line and for extension line calling, said method comprising operatively connecting the main unit to an external office line, operatively connecting the plurality of telephone sets to the main unit in parallel via three pairs of wires constituted by a first pair of line wires, a second pair of audio signal wires and a third pair of data signal wires, and supplying electrical voltage from an external source through the main unit to each of the telephone sets via the pairs of data wires and audio wires enabling extension line calling to be completed through said pair of audio signal wires and said pair of data signal wires whereas outside calling through the external office line is effected through the the line wires and the main unit.
Dependencies are inferred from the claim text.
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No related US applications are recorded in the indexed filing history.
Arrangements for interconnection not involving centralised switching: with subscriber controlled access to a line, i.e. key telephone systems
Telephonic communication
Term ended 3 Jan 2003 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
The present invention relates to key telephone equipment and associated methods, and more particularly, to a key telephone system making use of loudspeaker key telephone sets, in which the number of connecting wires between a main unit and the key telephone sets is minimized.
Heretofore, the aforementioned type of key telephone equipment has been conveniently used as a means for enabling a number of extension line telephone sets to use a common circuit of an office line. However, in such key telephone equipment it was necessary to use a large number of connecting wires for connecting the main unit to the respective key telephone sets.
As one solution for eliminating this shortcoming, it was proposed to use a control wire in common by every telephone set by carrying out transmission of a control signal with time-shared pulse signals, as disclosed in Japanese Patent Publication No. 52-48441. However, even in this improved system, a power supply line extending from a power supply to each telephone set was required. Moreover, in the case where a loudspeaker telephone set is used for each key telephone set, an audio signal line must be provided separately, and hence the number of connecting wires was further increased.
FIG. 1 is a block circuit diagram showing a construction of a main unit and telephone sets in one preferred embodiment of the present invention;
FIG. 2(a) shows the format of a transmission signal to be used for data transmission between the main unit and the telephone sets shown in FIG. 1;
FIG. 2(b) shows a pulse waveform of the same transmission signal on the data wires;
Referring now to FIG. 1, the illustrated embodiment comprises a main unit 1 connected to an office line and an A.C. power source, a plurality of key telephone sets (hereinafter called simply "telephone sets") 2-1, 2-2 . . . , 2-N (only two of them being illustrated) and a 6-wire cable 3 connecting the main unit 1 to the plurality of telephone sets 2-1, 2-2, etc. It is to be noted that all the telephone sets are connected in parallel to the 6-wire cable 3 as shown in FIG. 1. In other words, the 6-wire cable 3 is used in common for connecting each telephone set to the main unit, and accordingly the respective telephone sets are also connected to each other through the same 6-wire cable.
In the 6-wire cable 3, two wires l.sub.1 and l.sub.2 are used as office line call wires, two other wires a.sub.1 and a.sub.2 are used as audio signal wires, and the remaining two wires d.sub.1 and d.sub.2 are used as data wires. In addition, the two pairs of wires a.sub.1 and a.sub.2 and d.sub.1 and d.sub.2 are also jointly used to form an extension call line and a power supply line as will be described later. It is to be noted further that in place of the 6-wire cable 3, other multi-wire cables or a plurality of single-wire cables could be employed.
Construction of the Main Unit: