JPH0416551Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Industrial application field]

This invention relates to a device for determining whether a telephone is connected or not, for example, in an extension circuit of a private telephone system, for determining whether or not a telephone is connected to a connection terminal of a telephone of a terminal.

[Conventional technology]

For example, if the extension telephones of a local telephone system are connected using screws, general users would not normally be able to attach or detach the telephones. For this reason, the telephone itself did not have a removable terminal, and once the telephone installation work was completed, there was no need to determine whether the terminal telephone was connected unless there were special circumstances.

[Problem that the idea aims to solve]

However, telephones with modular connection terminals such as plugs or jacks have become widespread, allowing users to freely and easily attach and detach the telephone. There is. When such a telephone that is easy to attach and detach is used as a terminal telephone of a private telephone system equipped with a private branch exchange used in a hotel or the like, the following problems may occur. In other words, in the private telephone system used in hotels and the like, a telephone terminal is installed in each room, but if this telephone uses the modular connection terminal described above, it is easy to unplug it from the modular jack. Since the phone can be removed by simply unplugging it, there is a risk that the phone could be stolen. Therefore, for example, if the front desk of a hotel could determine whether the telephone terminal in each room is connected to the modular terminal or not, it would be possible to effectively deal with the above situation, and it would be convenient. It is. In view of the above points, this invention aims to provide a device that can easily determine whether or not a telephone is connected.

[Means to solve the problem]

The device for determining whether or not a telephone is connected includes a first switch circuit provided between a connection terminal to which a telephone is connected and a power supply circuit that supplies power to the telephone; when a telephone is connected to the connection terminal; a series circuit of a second switch circuit and a detection means including a detection element for detecting whether or not the telephone is connected to a connection terminal, which is connected in parallel to the telephone; a switch control circuit that performs switching control on the switch circuit in accordance with the operation of the manual switch; a determination start means for supplying a start signal for determining whether or not a telephone is connected to the switch control circuit; The present invention includes a determining means for determining whether or not the present invention is true, and a notifying means for receiving the output of the determining means and notifying the result of the determination.

[Effect]

Under normal conditions, the switch control circuit
The first switch circuit is on, and the second switch circuit is off. At this time, if the telephone is connected to the connection terminal, the capacitance of the telephone is charged. Next, the determination start means is operated. Then, the control circuit turns off the first switch and turns on the second switch circuit. If the telephone is connected at this time, a discharge current flows through the detection means from the capacitance of the telephone, and this discharge current is detected by the detection means. If the telephone is not connected, no discharge current will flow, so the determination circuit determines whether or not the telephone is connected to the connection terminal based on the output of this detection means. Then, the determination output is supplied to the notification means, and the determination result is notified. Therefore, it is possible to easily confirm whether or not the telephone is connected by this notification means.

【Example】

FIG. 1 is a block diagram of an embodiment of this invention.
FIG. 2 is a time chart for explaining this. In FIG. 1, 1 is a power supply circuit, 2A and 2B are telephone connection terminals, and the connection terminals 2A and 2B are modular terminals. A telephone 3 will be connected between the connection terminals 2A and 2B. When the telephone 3 is connected, power is supplied to the telephone 3 from the power supply circuit 1. A first switch circuit 4 is connected between one of the connection terminals 2A and 2B, in this example, between the connection terminal 2A and the power supply circuit 1. Further, a series circuit of a second switch circuit 5 and a detection means 6 including a detection element for detecting whether or not a telephone is connected is connected between the connection terminals 2A and 2B. When the telephone 3 is connected between the connecting terminals 2A and 2B, the series circuit of the second switch circuit 5 and the detection means 6 is connected in parallel with the telephone 3. In this example, the detection element of the detection means 6 is:
A photocoupler 63 consisting of a light emitting diode 61 and a phototransistor 62 for receiving light is used. 64 is a current limiting resistor, 65 is a power supply terminal, 6
6 is a load resistance. 7 is a switch control circuit from which switching control signals SW1 and SW2 are obtained, and the first and second switch circuits 4 and 5 are controlled by switching control signals SW1 and SW2. Reference numeral 71 denotes a manual switch as an example of determination starting means, and when this is operated, the states of the switching control signals SW1 and SW2 are reversed. 8 is a judgment circuit which receives the output of the detection means 6 and
It is determined whether the telephone 3 is connected between the connection terminals 2A and 2B. Reference numeral 9 denotes a display means which receives the judgment output from the judgment circuit 8 and displays the judgment result as to whether or not the telephone 3 is connected between the connection terminals 2A and 2B. This display means 9 is, for example, a light emitting diode, a lamp,
It may be configured with an LED or the like, or the display means may be configured with a liquid crystal display to display the determination result in characters. A determination end signal is obtained from the determination circuit 8, and this is supplied to the switch control circuit 7, which controls the switch circuit 4.
and 5 are reset to steady state. The discriminating operation by the discriminating device having the above configuration will be explained below. First, in a steady state, the first switch circuit 4 is turned on by the switching control signal SW1 (FIG. 2A) from the switch control circuit 7, and
The second switch circuit 5 is turned off by the switching control signal SW2 (FIG. 2B). In this state, if the telephone 3 is connected between the connection terminals 2A and 2B, power is supplied from the power supply circuit 1 to the telephone 3, so that the capacitance of the telephone 3 is charged. Next, when it is desired to determine whether or not the telephone 3 is connected between the connection terminals 2A and 2B, the manual switch 71 is pressed. Then, the switching control signals SW1 and SW2 from the switch control circuit 7
reverses the state, as shown in FIGS. 2A and 2B. Therefore, the first switch circuit 4 is off,
The second switch circuit 5 is turned on. At this time,
If the telephone 3 is connected between the connection terminals 2A and 2B, the capacitance of the telephone 3 is charged, so this capacitance is discharged, and the discharge current flows through the second switch circuit 5. The light flows through the resistor 64 to the light emitting diode 61, and the light emitting diode 61 emits light. The light emitting diode 61 continues to emit light for a time T ₁ until the capacitance of the telephone 3 is completely discharged. For this reason, the phototransistor 62
is on during this time _T1 , and its collector output voltage SD goes low during this time _T1 , as shown in FIG. 2C. On the other hand, when the telephone 3 is not connected between the connection terminals 2A and 2B, there is no charged capacitance of the telephone 3, so almost no current flows through the light emitting diode 61, and the output voltage SD of the detection means 6
is as shown in FIG. 2D, and the switch circuit 5
The time it takes to go low after being turned on is almost a short time T ₂ or almost zero. The output voltage SD of the detection means 6 is supplied to the determination circuit 8. The determination circuit 8 detects the length of time that the detection output voltage SD of the detection means 6 is at a low level, and the length of time that the detection output voltage SD of the detection means 6 is at a low level is T ₂
When it is determined that T ₀ is longer than T ₀ < T 0 < T ₁ ,
It is determined that the telephone 3 is connected between the connection terminals 2A and 2B, and when it is determined that the length is shorter than T ₀ ,
It is determined that the telephone 3 is not connected between the connection terminals 2A and 2B. This determination output is supplied to the display means 9. For example, when it is determined that the telephone 3 is connected, a display element such as a lamp or a light emitting diode is lit, and when it is determined that the telephone 3 is not connected, a display element such as a lamp or a light emitting diode is lit. , these light emitting elements remain off. Green when phone 3 is connected;
The color of the light emitted by the display element may be changed, such as red when the telephone 3 is not connected. The determination circuit 8 also supplies an end signal to the switch control circuit 7 when the determination is completed.
When the switch control circuit 7 receives this termination signal, it resets the switching signals SW1 and SW2 to a steady state. Therefore, the first switch circuit 4 is turned on and the second switch circuit 5 is turned off. In this way, it is possible to easily determine whether or not the telephone 3 is connected between the connection terminals 2A and 2B by simply looking at the display on the display means 9. FIG. 3 shows another embodiment of this invention, which differs from the example shown in FIG. 1 in the configuration of the detection means 6 and the configuration of the determination circuit. That is, in this example, the detection element of the detection means 6 is constituted by a parallel circuit of a capacitor 67 and a switch circuit 68, and this parallel circuit is connected in series with the second switch circuit 5. The switch circuit 68 is
Switching control signal from switch control circuit 7
Switching is controlled by SW1 in the same way as the first switch circuit 4. Then, the voltage EC across the capacitor 67 of the detection means 6 is output to the determination circuit 1 as the detection output voltage.
0. The determination circuit 10 determines from the value of the voltage EC across the capacitor 67 whether the telephone 3 is connected between the connection terminals 2A and 2B. The determination operation will be explained below. In the steady state, switch circuits 4 and 68 are turned on and switch circuit 5 is turned off by switching control signals SW1 and SW2 (FIGS. 4A and 4B). Therefore, the capacitor 67 of the detection means 6 is discharged via the switch circuit 68, and the voltage EC across it is approximately zero. Further, at this time, if the telephone 3 is connected between the connection terminals 2A and 2B, power is being supplied to the telephone 3 from the power supply circuit 1, so that the capacitance of the telephone 3 is charged. From this state, push the manual switch 71 to turn it on. Then, the output signal SW1 of the switch circuit 7
and SW2 are inverted, switch circuits 4 and 68 are turned off, and switch circuit 5 is turned on. Therefore, if the telephone is connected between the connection terminals 2A and 2B, the capacitance of the telephone is discharged and a charging current flows to the capacitor 67 of the detection means 6, and the voltage EC across the capacitor 67 is equal to the static capacitance of the telephone. It becomes equal to the voltage across the capacitance (Fig. 4C). If the telephone 3 is not connected, the capacitor 67 is not charged, so the voltage EC across it remains approximately zero. The determination circuit 10 compares this voltage EC with a predetermined threshold value VT, and if the voltage EC is higher than this threshold value VT, it determines that the telephone 3 is connected between the connection terminals 2A and 2B, and the voltage EC is higher than the threshold value VT. If it is lower than this threshold value VT, it is determined that the telephone 3 is not connected between the connection terminals 2A and 2B. The display means 9 receives the judgment output from the judgment circuit 10 and displays the judgment result in the same manner as the example in FIG. Further, when the determination is completed, a termination signal from the determination circuit 10 causes the switch control circuit 7 to
is reset and switch circuits 4, 5 and 68
returns to steady state. In the above example, the display means was used as a means of notifying the judgment result, but the judgment result may be notified by sound, such as by sounding a buzzer when the telephone is not connected, or by other various methods. Notification means can be used. Further, in the above example, a manual switch is provided for the switch control circuit 7, and the discrimination operation is started by operating the switch of this means, but the signal for starting the discrimination operation is The determining operation starting means may be any operating means as long as it is supplied to the switch control circuit 7.

[Effect of the idea]

According to this invention, with a simple circuit configuration, it is possible to determine whether or not the telephone is connected to the connection terminal whenever necessary. Therefore, no one will mistake the fact that the telephone is not connected to be malfunctioning. Furthermore, when there is a risk that the telephone may be stolen, by appropriately operating the discrimination start means, it can be determined that the telephone has been disconnected from the connection terminal, thereby making it possible to prevent theft.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of this invention.
2 is a time chart for explaining the operation of the example in FIG. 1, FIG. 3 is a block diagram of another example of this invention, and FIG. 4 is a time chart for explaining the operation of the example in FIG. It is. 1...Power supply circuit, 2A, 2B...Connection terminal, 3
...Telephone, 4, 5...Switch circuit, 6...Telephone connection detection means, 7...Switch control circuit,
8, 10... Circuit for determining whether or not a telephone is connected, 9...
Display means.

Claims (1)

[Claims for Utility Model Registration] A first switch circuit provided between a connection terminal to which a telephone is connected and a power supply circuit that supplies power to the telephone; a series circuit of a second switch circuit and a detection means including a detection element for detecting whether or not the telephone is connected to a connection terminal, the first and second switch circuits being connected in parallel to each other; a switch control circuit that performs switching control; a determination start means that supplies a start signal for determining whether a telephone is connected to the switch control circuit; and a determination means that receives the output of the detection means and determines whether or not a telephone is connected. , and notification means for receiving the output of the determination means and notifying the determination result.