JPH01209852A - Busy state detector for parallel connection telephone set and privacy call device - Google Patents

Abstract

PURPOSE:To display the busy state of other telephone set connected in parallel and to disable the use of its own telephone set at busy state by providing a voltage detection means to an output terminal of a rectifier of the telephone set connected in parallel and discriminating the level of the voltage detection means. CONSTITUTION:A voltage distribution means 3 comprising resistors R1, R2 and a Zener diode ZD is connected to the output of a rectifier circuit R. The potential level at the middle point of the voltage distribution means 3 is discriminated by a logic circuit 6 and when the potential level is low, it is discriminated that other telephone set T2 connected in parallel is busy, a hook switch 8 is turned off to disable the telephone set circuit 2. Furthermore, a busy display lamp 4 is connected to the middle point of the voltage distribution means 3. The busy state display lamp 4 is lighted when the level of the middle point of the voltage distribution means 3 is at a low level, that is, the other telephone set T2 is busy to display the busy state of the other telephone set.

Description

[Detailed Description of the Invention] [Industrial Application Field J] The present invention provides a method for connecting a plurality of telephones in parallel to one telephone line, and when one telephone is busy, other telephones The present invention relates to a busy detection device and a privacy device for parallel-connected telephones, which display an indication that the telephone is busy, and have a function of interlocking the telephones.

[Prior Art] ' Conventionally, by connecting two or more telephones in parallel to one telephone line, it is possible to make and receive calls from any telephone, and it is possible to make and receive calls from any telephone without increasing the number of lines. 1 for the location! It was possible to install and use a telephone.

[Problems to be Solved by the Invention] When using the conventional parallel-connected telephone described above, it was necessary to pick up the handset and check whether another telephone was in use or not by checking whether there was voice on the call, etc. . For that reason,
There have been cases in which a caller who is already using the service is disturbed by the generation of noise or a drop in the voice level. Furthermore, it has been difficult to keep the contents of telephone calls confidential.

The present invention has been made to solve the problems related to the conventional parallel-connected telephones described above, and is a simple device that can
It is an object of the present invention to provide a busy detection device and a privacy device for parallel-connected telephones, which have a function to display when the telephone is busy and to communicate secretly to each other, and which make the use of parallel-connected telephones smoother and more effective. It is something.

[Means for Solving the Problems] In order to solve the above-mentioned problems and achieve the above objects, a busy detection device and a secret device for parallel-connected telephones according to the present invention provide a device for detecting direct current from a telephone line. In a telephone circuit comprising a rectifier circuit to obtain a voltage, and another telephone circuit, a voltage distribution means for distributing the output voltage is connected to the output side of the rectification circuit, and an intermediate point of the voltage distribution means. In a telephone circuit having a configuration in which a busy mode lamp is provided, a rectifier circuit that obtains DC voltage from a telephone line, and other telephone circuits, the output side of the rectifier circuit is a voltage distribution means for distributing the output voltage; a logic circuit for determining a potential level at an intermediate point of the voltage distribution means to be a high level or a low level; and turning on a line leading to the other telephone circuit according to the judgment of the logic circuit The structure is provided with a switch to turn it off.

Preferably, the voltage distribution means includes a Zener diode, and the logic circuit receives an operation signal of a hook switch for detecting the state of the handset in the telephone circuit; Preferably, the logic circuit makes a decision based on the potential level at the midpoint of the voltage distribution means.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below based on embodiments. The drawings are schematic explanatory diagrams showing one embodiment of the present invention. R is a rectifier circuit consisting of a bridge type etc. which obtains the DC voltage EV from the telephone lines L1 and L2 connected to the telephone exchange, and 1
Other telephone Higuchi HI required for normal telephone functions
2 constitutes the telephone circuit 1. In the present invention, a voltage distribution means 3 for distributing the output voltage is provided on the output side of the rectifier circuit R, and a lamp 4 of the busy phase connected to an intermediate point A of the voltage distribution means 3 is provided. It is intended to provide 5 is the inverter (N
T, which is an OT circuit), is another telephone (there may be more than one) connected in parallel to the telephone line L, similar to the telephone T1 made of the telephone circuit 1.

The main components of the voltage distribution means 3 are resistors R2, R2, and a Zener diode ZD is connected in series with R1. In addition, in accordance with the telecommunications law, 1 line L
When 1 and L are open, the insulation resistance between the lines Li and L has a value of 1 MΩ or more at 250 V DC.

Then, line L1. L is open.

That is, when all telephones are in standby mode, line L1.52
A potential of about 48 V appears between them, and the output voltage E of the rectifier circuit R is a high voltage equivalent to about 48 V. The potential at the midpoint A of the voltage distribution means 3 becomes a high level, and the inverter Lamp 4 provided at a suitable position on telephone T1
is kept in a non-lit state. Next, when the telephone T2 is in use, the lines 4 and L8 are closed, and in this state the output voltage E of the rectifier circuit R is about 26V at maximum, and normally it is 12V to 1.5V (via the exchange). As a result, the potential at point A becomes a low level, and the inverter 5 turns on the lamp 4, indicating that the other telephone is "in use." indicate. Zener diode ZD
By appropriately selecting the breakdown voltage of , it is possible to more clearly distinguish between high and low potentials at the intermediate point A, which vary depending on the open and closed states of one line.

Furthermore, in the present invention, the intermediate point A of the voltage distribution means 3
A logic circuit 6 determines whether the potential level of is high or low, and the logic circuit 6 determines that the potential level is high or low.

A switch SW can be provided to turn on and off lines leading to other telephone circuits 2. That is, the logic circuit 6
As mentioned above, when the lines L1 and R2 are open, the intermediate point A is determined to be at a high level, the switch SW is turned on, and the telephone T1 is placed in a usable standby state. If another telephone such as T1 is in use, intermediate point A is determined to be a low level, the switch SW is turned off, and even if the handset of telephone circuit 1 is picked up, the call voice from other telephones such as T2 will not be heard. is not considered audible,
Demonstrates secret function. In the figure, H8 is a hook switch for detecting the state of the handset, which can apply an input to the logic circuit 6 according to the state of the handset in the above-mentioned telephone circuit 1 (off-hook, lowered, on-hook). .

That is, when another telephone such as Ts is in use, even if the handset is picked up and the hook switch H8 input is applied to the logic circuit 6, the potential level (low level) at the intermediate point A According to the logical operation of the logic circuit 6, the switch SW is
When all the telephones such as T1 and T2 are not in use and you pick up the handset of telephone T1 and start using it, the input of hook switch H8 is applied and the previous state is set. In combination with the potential level (high level) at the intermediate point A, the switch SW is held in the on state by the logical operation of the logic circuit 6, and the telephone T1 can be used. It goes without saying that by arranging the Zener diode ZD in the voltage distribution means 3, the high and low potential levels at the intermediate point A can be clearly distinguished, which is advantageous for the operation of the logic circuit 6.

[Operations and Effects of the Invention] In the busy detection device for parallel-connected telephones of the present invention having the above-described configuration, voltage distribution means is provided for distributing the output voltage of the rectifier circuit, and the potential level at the intermediate point A is Since the level changes to low or high depending on whether the parallel-connected telephone is in use or not, a simple device can detect this change and turn the busy main phase lamp on or off. This makes it possible to check whether other parallel-connected telephones are in use without having to pick up the handset when using a telephone, without disturbing other telephone users.
It can be grasped immediately and reliably.

Similarly, in the secret communication device for parallel-connected telephones according to the present invention, it is simple to use a switch that operates based on a logic circuit's judgment based on changes in the potential level at intermediate point A to turn off or on other telephone circuits. This is possible with a device that is connected in parallel to one line, and the contents of a call made during use by any telephone set that is connected in parallel to one line cannot be intercepted by other telephone sets, so that the contents of the call are kept confidential.

By disposing a Zener diode in the voltage distribution means, high and low potential levels at the intermediate point A can be distinguished more clearly, and lamp blinking operations and logic circuit judgments can be made accurately without mistakes. It is something. Further, by inputting the operation signal of the hook switch to the logic circuit, the operational functions of the telephone according to the present invention having a private conversation function are completed.

[Brief explanation of the drawing]

The drawings are schematic explanatory diagrams showing one embodiment of the present invention.

Claims (4)

[Claims] (1) In a telephone circuit comprising a rectifier circuit that obtains DC voltage from a telephone line and another telephone circuit, voltage distribution means for distributing the output voltage to the output side of the rectifier circuit; A busy detection device for parallel-connected telephones, characterized in that a busy display lamp is connected to an intermediate point of a voltage distribution means. (2) In a telephone circuit comprising a rectifier circuit that obtains DC voltage from a telephone line and another telephone circuit, voltage distribution means for distributing the output voltage to the output side of the rectifier circuit; A logic circuit that determines the potential level at the intermediate point of the voltage distribution means to be a high level or a low level, and a switch that turns on or off a line leading to the other telephone circuit according to the determination of the logic circuit. Confidential device for parallel connected telephones. (3) A busy detection device and a privacy device for parallel-connected telephones according to claim 1 or 2, wherein the voltage distribution means includes a Zener diode. (4) The operation signal of the hook switch for detecting the status of the handset in the telephone circuit is input to the logic circuit, and the logic circuit makes a decision based on the potential level at the midpoint between the input and the voltage distribution means. 3. A secret device for parallel-connected telephones according to claim 2.