JPH0269095A - Device for controlling current distribution to key telephone set of key telephone system - Google Patents

Device for controlling current distribution to key telephone set of key telephone system

Info

Publication number
JPH0269095A
JPH0269095A JP21964388A JP21964388A JPH0269095A JP H0269095 A JPH0269095 A JP H0269095A JP 21964388 A JP21964388 A JP 21964388A JP 21964388 A JP21964388 A JP 21964388A JP H0269095 A JPH0269095 A JP H0269095A
Authority
JP
Japan
Prior art keywords
current
main device
supplied
button telephone
circuit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP21964388A
Other languages
Japanese (ja)
Inventor
Kazuo Ihata
井幡 和夫
Takumi Oikawa
巧 及川
Takeki Sugai
菅井 勇樹
Motomasa Igarashi
五十嵐 基正
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NEC Platforms Ltd
Original Assignee
Nitsuko Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nitsuko Corp filed Critical Nitsuko Corp
Priority to JP21964388A priority Critical patent/JPH0269095A/en
Publication of JPH0269095A publication Critical patent/JPH0269095A/en
Pending legal-status Critical Current

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Abstract

PURPOSE:To make the electric current supplied from a main device always smaller in current value by connecting plural current controlling elements with each other in series through a constantcurrent circuit against a current supplying line and corresponding short-circuiting circuits in parallel with each other to the plural current elements. CONSTITUTION:Turning on and turning off of N pieces of short-circuiting circuits 42-1 to 42-N are controlled by means of a control circuit 44. As a result, supply of an electric current Icc to current controlling elements 41-1 to 41-N from the power supplying source 11 of a main device 10 through a current supplying line 30 is controlled. A Zener diode 45 is connected in parallel with the control circuit 44. Therefore, the power supply source 11 of the main device 10 can always supply an electric current equal to the electric current IL which flows to the current controlling elements connected in parallel with the short- circuiting circuits when the short-circuiting circuits are turned off by the control circuit 44 as the electric current lcc supplied to a current distribution controller 40 through the line 30.

Description

【発明の詳細な説明】 [産業上の利用分野] 本発明は、主装置と、主装置に接続された複数のボタン
74 g8機とから成るボタン電話システムに関し、特
に、主装置から複数のボタン電話機の各々に電流供給線
を介して電流が供給され、この供給された電流を各ボタ
ン電話機に設けられた複数の電流制御素子へ分配する制
御を行うボタン電話機の電流分配制御装置に関する。
Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a button telephone system comprising a main device and a plurality of buttons 74g8 connected to the main device, and in particular, The present invention relates to a current distribution control device for a button telephone, in which current is supplied to each of the telephones via a current supply line, and the supplied current is distributed to a plurality of current control elements provided in each button telephone.

[従来の技術ゴ 一般に、ボタン電話システムは、第2図に示されるよう
に、主装置10と、主装置10に接続された複数のボタ
ン電話機(図面では1つのボタン電話機20のみ図示す
る。)とから成る。主装置10は、各ボタン電話機20
へ電流を供給するための電流供給源11を有する。電流
供給源11からの電流は、一対の電流供給線30を介し
て、各ボタン電話機20へ供給される。従って、各ボタ
ン電話機20は、主装置10から一対の電流供給線30
を介して供給される電流を供給された電流I ccとし
て受ける。そして、各ボタン電話機20は、この供給さ
れた電流Iceを、自ボタン電話機に設けられた発光ダ
イオード(以下、LEDと略称する。)やフォトカブラ
等の複数の電流制御素子へ分配する制御を行う電流分配
制御装置を備えている。
[Prior Art] In general, a button telephone system, as shown in FIG. 2, includes a main device 10 and a plurality of button telephones connected to the main device 10 (only one button telephone 20 is shown in the drawing). It consists of The main device 10 includes each button telephone 20
It has a current supply source 11 for supplying current to. Current from the current supply source 11 is supplied to each button telephone 20 via a pair of current supply lines 30. Therefore, each button telephone 20 is connected to a pair of current supply lines 30 from the main device 10.
The current supplied through the terminal is received as the supplied current Icc. Then, each button telephone 20 performs control to distribute the supplied current Ice to a plurality of current control elements such as a light emitting diode (hereinafter abbreviated as LED) and a photocoupler provided in the own button telephone. Equipped with a current distribution control device.

尚、周知のように、一対の電流供給線30は、主装置1
0と各ボタン電話機20との間でデータ伝送を行うため
のデータ伝送線としても用いられる。
As is well known, the pair of current supply lines 30 are connected to the main device 1.
It is also used as a data transmission line for transmitting data between 0 and each button telephone 20.

従来の電流分配制御装置40′では、第2図に示される
ように、複数(例えば、N個)の電流制iaa素子41
−1.41−21.、− 4l−(N−1)、及び41
−Nの各々は一対の電流供給線30間に接続されている
。換言すると、N個の電流制御素子41−1〜41−N
は、互いに並列に接続されている。電流制御索子41−
1〜41−Nには、それぞれ、直列にショート回路42
−1.42−2、・・・ 42− (N−1) 、及び
42−Nと、抵抗43−1.43−2、・・・、43−
(N−1)、及び43−Nとが接続されている。このN
個のショート回路42−1〜43−Nは、一対の電流供
給線30間に接続されている制御回路44によってオン
・オフ制御され、これにより、主装置10の電流供給源
11から電流供給線30を介して供給された電流I c
eの電流制御素子41−1〜41−Nへの供給が制御さ
れる。尚、周知の方法で、制御回路44には、主装置1
0の制御回路(図示せず)より発生された命令が、電流
供給線30を介してのデータ伝送によって供給され、制
御回路44は、この命令に従ってショート回路42−1
〜43−Nの制御を行う。
In the conventional current distribution control device 40', as shown in FIG.
-1.41-21. , -4l-(N-1), and 41
-N are each connected between a pair of current supply lines 30. In other words, N current control elements 41-1 to 41-N
are connected in parallel with each other. Current control cable 41-
A short circuit 42 is connected in series to each of 1 to 41-N.
-1.42-2,... 42- (N-1), and 42-N, and resistor 43-1.43-2,..., 43-
(N-1) and 43-N are connected. This N
The short circuits 42-1 to 43-N are controlled on/off by a control circuit 44 connected between the pair of current supply lines 30, and thereby the current supply lines from the current supply source 11 of the main device 10 The current I c supplied through 30
The supply of e to the current control elements 41-1 to 41-N is controlled. Note that, in a well-known manner, the control circuit 44 includes the main device 1.
A command generated by a control circuit 42-1 (not shown) is supplied by data transmission via the current supply line 30, and the control circuit 44 operates the short circuit 42-1 according to this command.
-43-N are controlled.

ここで、制御回路44には、IcO値をもつ電流が常時
供給される必要があり、各電流制御素子には、それに直
列に接続されたショート回路が制御回路44によってオ
ンにされた時に、ILの値をもつ電流を流す必要がある
Here, it is necessary to constantly supply a current having an IcO value to the control circuit 44, and when a short circuit connected in series with each current control element is turned on by the control circuit 44, the IL It is necessary to flow a current with a value of .

[発明が解決しようとする課題] 上述したように、従来の電流分配制御装置40’では、
N個の電流制御素子41−1〜41−Nが互、いに並列
に接続されており、制御回路44も一対の電流供給線3
0間に接続されているので、主装置10の電流供給源1
1は、ボタン電話機20の電流分配制御装置40’へ、
最大Iccmax −Nx IL +Icの値をもつ電
流I ceを供給する必要がある。一般に、ボタン電話
システムでは、各ボタン電話機には数多くの電流制御素
子が設けられている、即ち、Nが大きいので、従来の電
流分配制御装置40’では、電流制御素子の数Nが増加
すればするほど、電流分配制御装置40′に供給される
電流Iccの値が大きくなり、換言すれば、主装置10
はボタン電話機20へ大きな値をもつ電流1 ccを供
給しなければならず、電流供給源11としての大容量の
ものを使用しなければならないという欠点がある。また
、この供給される電流Iceが増加するということは、
電流供給線30において、その抵抗骨により不要な電力
を消費する割合いが大きくなることを意味する。
[Problems to be Solved by the Invention] As described above, in the conventional current distribution control device 40',
N current control elements 41-1 to 41-N are connected in parallel, and the control circuit 44 also connects to a pair of current supply lines 3.
0, so the current supply source 1 of the main device 10
1 to the current distribution control device 40' of the button telephone 20;
It is necessary to supply a current I ce with a maximum value of Iccmax −Nx IL +Ic. Generally, in a button telephone system, each button telephone is provided with a large number of current control elements, that is, N is large, so in the conventional current distribution control device 40', as the number N of current control elements increases, The more the current Icc is supplied to the current distribution control device 40', the larger the value of the current Icc is.
has the disadvantage that it is necessary to supply 1 cc of current with a large value to the button telephone 20, and that a large capacity current supply source 11 must be used. In addition, this increase in the supplied current Ice means that
This means that in the current supply line 30, the rate of unnecessary power consumption increases due to its resistance.

従って、従来の電流分配制御装置40′を備えたボタン
電話システムでは、電流供給線30での電力消費を少な
くするために、主装置10とボタン電話機20との間を
接続する電流供給線30の伝送距離を短くしなければな
らないという欠点がある。
Therefore, in a button telephone system equipped with a conventional current distribution control device 40', in order to reduce power consumption in the current supply line 30, the current supply line 30 connecting between the main device 10 and the button telephone 20 is The disadvantage is that the transmission distance must be shortened.

従って、本発明の目的は、主装置から供給される電流の
値が小さくても、確実に、その供給された電流を複数の
電流制御素子に分配制御することができるボタン電話機
の電流分配制御装置を提供することにある。
Therefore, an object of the present invention is to provide a current distribution control device for a button telephone that can reliably distribute and control the supplied current to a plurality of current control elements even if the value of the current supplied from the main device is small. Our goal is to provide the following.

本発明の他の目的は、主装置とボタン電話機との間を接
続する電流供給線の伝送距離が長くても、主装置から供
給された電流を、確実に、複数の電流制御素子に分配制
御することができるボタン電詰機の電流分配制御装置を
提供することにある。
Another object of the present invention is to reliably control the distribution of current supplied from the main device to a plurality of current control elements even if the transmission distance of the current supply line connecting the main device and the button telephone is long. An object of the present invention is to provide a current distribution control device for a button electric packing machine.

[課題を解決するための手段] 本発明によるボタン電話システムにおけるボタン電話機
の電流分配制御装置は、主装置と、該主装置に接続され
た複数のボタン電話機とから成るボタン電話システムに
おける、前記複数のボタン電話機の各々に設けられ、前
記主装置からの電流を電流供給線を介して供給された電
流として受け、該供給された電流を定電流回路を介して
複数の電流制御素子に分配するための制御を行う電流分
配制御装置であって、前記複数の電流制御素子にそれぞ
れ対応して設けられた複数のショート回路と、該複数の
ショート回路のオン・オフを制御することにより、前記
複数の電流制御素子への前記供給された電流の供給を制
御する制御回路とを有している前記電流分配制御装置に
おいて、前記複数の電流制御素子を前記定電流回路を介
して前記電流供給線に対して直列に接続し、前記複数の
電流制御素子の各々に、対応するショート回路を並列に
接続したことを特徴とする。
[Means for Solving the Problems] A current distribution control device for a button telephone in a button telephone system according to the present invention is a current distribution control device for a button telephone in a key telephone system, which is a key telephone system comprising a main device and a plurality of key telephones connected to the main device. provided in each of the button telephones, for receiving the current from the main device as a current supplied via a current supply line, and distributing the supplied current to a plurality of current control elements via a constant current circuit. A current distribution control device that controls a plurality of short circuits provided corresponding to each of the plurality of current control elements, and by controlling on/off of the plurality of short circuits. and a control circuit that controls supply of the supplied current to the current control element, the plurality of current control elements being connected to the current supply line via the constant current circuit. The plurality of current control elements are connected in series, and a corresponding short circuit is connected in parallel to each of the plurality of current control elements.

〔作 用] 複数の電流制御素子が電流供給線に対して直列に接続さ
れているので、主装置から電流供給線を介してボタン電
話機の電流分配制御装置に供給される電流の値t cc
は、各電流制御装置に必要とされる電流ILと等しく、
一定である。換言すると、各電流制御素子にはショート
回路が並列に接続されているが、ショート回路の中の1
つが制御回路によりオンされ、それに対応する電流制御
素子への電流供給がなくなっても、定電流回路により残
りの電流制al;4:子へは値ILの電流が流れること
になる。従って、従来のように、複数の電流制御素子が
互いに並列接続されている電流分配制御装置に比較して
、本発明のように、複数の電流制御素子を電流供給線に
対して直列に接続した電流分配制御装置の方が、主装置
から供給される電流は、常に小さい電流値ですむ。これ
により、本発明による電流分配制御装置を備えたボタン
電話システムでは、主装置に備えられる電流供給源は小
容量のものでよく、また、主装置とボタン電話機との間
を接続する電流供給線の伝送距離が長くても、確実に、
主装置から供給された電流を、複数の電流制御素子に分
配制御することができる。
[Function] Since the plurality of current control elements are connected in series to the current supply line, the value t cc of the current supplied from the main device to the current distribution control device of the button telephone via the current supply line.
is equal to the current IL required by each current control device,
constant. In other words, short circuits are connected in parallel to each current control element, but one of the short circuits
Even if one is turned on by the control circuit and current is no longer supplied to the corresponding current control element, a current of value IL will flow to the remaining current control element by the constant current circuit. Therefore, compared to a conventional current distribution control device in which a plurality of current control elements are connected in parallel to each other, the present invention has a plurality of current control elements connected in series with a current supply line. With the current distribution control device, the current supplied from the main device always requires a smaller current value. As a result, in the button telephone system equipped with the current distribution control device according to the present invention, the current supply source provided in the main device may have a small capacity, and the current supply line connecting between the main device and the button telephone Even if the transmission distance is long,
The current supplied from the main device can be distributed and controlled to a plurality of current control elements.

[実施例コ 以下、本発明の実施例について図面を参照して説明する
[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

第1図を参照すると、本発明の一実施例による電流分配
制御装置40は、ボタン電話機20に備えられ、主装置
10から一対の電流供給線30を介して供給される電流
を供給された電流leeとして受ける。電流分配制御装
置40は、この供給された電流Iceを、定電流回路4
6を介してボタン電話機20に設けられたLEDやフォ
トカプラ等の複数の電流制御素子へ分配する制御を行う
。ここで、LEDからの発光は、可視光として表示に利
用される。フォトカブラは、他の電源系の制御に主に利
用される。
Referring to FIG. 1, a current distribution control device 40 according to an embodiment of the present invention is provided in a button telephone 20 and is supplied with current supplied from a main device 10 through a pair of current supply lines 30. Accepted as a lee. The current distribution control device 40 transfers the supplied current Ice to the constant current circuit 4.
Control is performed to distribute the current to a plurality of current control elements such as LEDs and photocouplers provided in the button telephone 20 via 6. Here, the light emitted from the LED is used as visible light for display. Photocoupler is mainly used to control other power supply systems.

本実施例の電流分配制御装置40において、N個の電流
制御素子41−N、41−2、・・・、41(N−1)
、及び41−Nは、定電流回路46を介して電流供給線
30に対して直列に接続されている。N個の電流制御素
子41−1〜41−Nには、それぞれ、並列にショート
回路42−1.42−2、・・・、42− (N−1)
 、及び42−Nが接続されている。このN個のショー
ト回路42−1〜42−Nは、直列に接続されたN個の
電流制御素子41−1〜4l−N(N個のショート回路
42−1〜42−N)に直列に接続されている制御回路
44によってオン・オフ制御され、これにより、主装置
10の電流供給源11から電流供給線30を介して供給
された電流Iceの電流制御素子41−1〜41−Nへ
の供給が制御される。
In the current distribution control device 40 of this embodiment, N current control elements 41-N, 41-2, . . . , 41 (N-1)
, and 41-N are connected in series to the current supply line 30 via the constant current circuit 46. Short circuits 42-1, 42-2, ..., 42- (N-1) are connected in parallel to the N current control elements 41-1 to 41-N, respectively.
, and 42-N are connected. These N short circuits 42-1 to 42-N are connected in series to N current control elements 41-1 to 4l-N (N short circuits 42-1 to 42-N). On/off control is performed by the connected control circuit 44, whereby the current Ice supplied from the current supply source 11 of the main device 10 via the current supply line 30 is transmitted to the current control elements 41-1 to 41-N. supply is controlled.

本実施例において、制御回路44には、並列にツェナー
ダイオード45が接続されている。
In this embodiment, a Zener diode 45 is connected in parallel to the control circuit 44 .

このような構成において、前述したように、制御回路4
4には、Icの値をもつ電流が常時供給される必要があ
る。また、各電流制御素子には、それに並列に接続され
たショート回路が制御回路44によってオフにされた時
に、ILの値をもつ電流を流す必要がある。一般に、I
c<ILO関係があるので、第1図に示されるように、
制御回路44には常時1eの値の電流が流れ、それと並
列に接続されたツェナダイオード45には、(IL−1
c)の値の電流が常時流れる。
In such a configuration, as described above, the control circuit 4
4 needs to be constantly supplied with a current having a value of Ic. Further, it is necessary to cause a current having a value of IL to flow through each current control element when the short circuit connected in parallel thereto is turned off by the control circuit 44. In general, I
Since there is a relationship c<ILO, as shown in Figure 1,
A current with a value of 1e always flows through the control circuit 44, and a Zener diode 45 connected in parallel with it always has a current of (IL-1).
A current of value c) always flows.

このように、N個の電流制御素子41−1〜41−Nが
電流供給線30に対して直列に接続されているので、主
装置10の電流供給源11は、電流分配制御装置40に
電流供給線30を介して供給する電流Iceとして、シ
ョート回路が制御回路44によってオフされたときに、
そのショート回路に並列に接続されている電流制御素子
に流れる電流ILと等しい電流を、常時、流すだけで良
い。
In this way, since the N current control elements 41-1 to 41-N are connected in series to the current supply line 30, the current supply source 11 of the main device 10 supplies the current to the current distribution control device 40. As the current Ice supplied via the supply line 30, when the short circuit is turned off by the control circuit 44,
It is sufficient to constantly flow a current equal to the current IL flowing through the current control element connected in parallel to the short circuit.

従って、従来例の電流分配制御装置40′ (第2図)
に比較して、本実施例の電流分配制御装置40の方が、
主装置10から供給される電流として、常に小さい電流
値ですむ。これにより、本実施例の電流制御装置40を
備えたボタン電話システムでは1.主装置10の電流供
給源11として、小容量のものでよく、また、主電流1
0とボタン電話機20との間を接続する電流供給線30
の伝送距離が長くても、確実に、主装置10から供給さ
れた電流を、N個の電流制御装置41−1〜41−Nに
分配制御することができる。
Therefore, the conventional current distribution control device 40' (Fig. 2)
Compared to this, the current distribution control device 40 of this embodiment has
The current supplied from the main device 10 always requires a small current value. As a result, in the button telephone system equipped with the current control device 40 of this embodiment, 1. The current supply source 11 of the main device 10 may be of small capacity, and the main current 1
A current supply line 30 connecting between 0 and the button telephone 20
Even if the transmission distance is long, the current supplied from the main device 10 can be reliably distributed and controlled to the N current control devices 41-1 to 41-N.

[発明の効果] 以上説明したように、本発明によれば、ボタン電話機に
設けられる複数の電流制御素子を電流供給線に対して直
列に接続したので、主装置から電流供給線を介して供給
される電流としては、各電流制御素子に流されるべき電
流と等しい電流を流すだけで良いので、非常に小さい値
ですむ。従って、本発明による電流分配制御装置を備え
たボタン電話システムでは、主装置に備えられる電流供
給源は小容量のものでよく、主装置とボタン電話機との
間を接続する電流供給線の伝送距離を長くすること・が
可能となる。
[Effects of the Invention] As explained above, according to the present invention, the plurality of current control elements provided in the button telephone are connected in series to the current supply line, so that the current is not supplied from the main device via the current supply line. Since it is sufficient to flow a current equal to the current that should be flowed through each current control element, the current that is caused to flow needs only a very small value. Therefore, in the button telephone system equipped with the current distribution control device according to the present invention, the current supply source provided in the main device may be of small capacity, and the transmission distance of the current supply line connecting between the main device and the button telephone is It becomes possible to lengthen.

【図面の簡単な説明】[Brief explanation of the drawing]

m1図は本発明の一実施例によるボタン電話機の電流分
配制御装置の構成を示す回路図、第2図は従来のボタン
電話機の電流分配制御装置の構成を示す図である。 10・・・主装置、11・・・電流供給源、20・・・
ボタン電話機、30・・・電流供給線、40・・・電流
分配制御装置、41−1〜41−N・・・電流制御素子
、42−1〜42−N・・・ショート回路、44・・・
制御回路、45・・・ツェナーダイオード、46・・・
定電流回路。
FIG. m1 is a circuit diagram showing the configuration of a current distribution control device for a button telephone according to an embodiment of the present invention, and FIG. 2 is a diagram showing the configuration of a conventional current distribution control device for a button telephone. 10... Main device, 11... Current supply source, 20...
button telephone, 30... current supply line, 40... current distribution control device, 41-1 to 41-N... current control element, 42-1 to 42-N... short circuit, 44...・
Control circuit, 45... Zener diode, 46...
Constant current circuit.

Claims (1)

【特許請求の範囲】 1、主装置と、該主装置に接続された複数のボタン電話
機とから成るボタン電話システムにおける、前記複数の
ボタン電話機の各々に設けられ、前記主装置からの電流
を電流供給線を介して供給された電流として受け、該供
給された電流を定電流回路を介して複数の電流制御素子
に分配するための制御を行う電流分配制御装置であって
、前記複数の電流制御素子にそれぞれ対応して設けられ
た複数のショート回路と、該複数のショート回路のオン
・オフを制御することにより、前記複数の電流制御素子
への前記供給された電流の供給を制御する制御回路とを
有している前記電流分配制御装置において、 前記複数の電流制御素子を前記定電流回路を介して前記
電流供給線に対して直列に接続し、前記複数の電流制御
素子の各々に、対応するショート回路を並列に接続した
ことを特徴とするボタン電話システムにおけるボタン電
話機の電流分配制御装置。
[Scope of Claims] 1. In a button telephone system consisting of a main device and a plurality of button telephones connected to the main device, each of the plurality of button telephones is provided with an electric current from the main device. A current distribution control device that receives a current supplied via a supply line and performs control to distribute the supplied current to a plurality of current control elements via a constant current circuit, the current distribution control device controlling the plurality of current control elements. a plurality of short circuits provided corresponding to the elements, and a control circuit that controls supply of the supplied current to the plurality of current control elements by controlling on/off of the plurality of short circuits; In the current distribution control device, the plurality of current control elements are connected in series to the current supply line via the constant current circuit, and each of the plurality of current control elements has a corresponding one. 1. A current distribution control device for a button telephone in a button telephone system, characterized in that short circuits are connected in parallel.
JP21964388A 1988-09-03 1988-09-03 Device for controlling current distribution to key telephone set of key telephone system Pending JPH0269095A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP21964388A JPH0269095A (en) 1988-09-03 1988-09-03 Device for controlling current distribution to key telephone set of key telephone system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP21964388A JPH0269095A (en) 1988-09-03 1988-09-03 Device for controlling current distribution to key telephone set of key telephone system

Publications (1)

Publication Number Publication Date
JPH0269095A true JPH0269095A (en) 1990-03-08

Family

ID=16738743

Family Applications (1)

Application Number Title Priority Date Filing Date
JP21964388A Pending JPH0269095A (en) 1988-09-03 1988-09-03 Device for controlling current distribution to key telephone set of key telephone system

Country Status (1)

Country Link
JP (1) JPH0269095A (en)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5171703A (en) * 1974-12-19 1976-06-21 Iwatsu Electric Co Ltd Botandenwasochini okeru kashihyojiseigyokairo
JPS51126701A (en) * 1975-04-25 1976-11-05 Toshiba Corp Display of a key telephone

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5171703A (en) * 1974-12-19 1976-06-21 Iwatsu Electric Co Ltd Botandenwasochini okeru kashihyojiseigyokairo
JPS51126701A (en) * 1975-04-25 1976-11-05 Toshiba Corp Display of a key telephone

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