JPH02140040A - Handset mounting detection circuit - Google Patents

Abstract

PURPOSE:To detect the presence of the mounting of a handset to a call circuit section without provision of a detection circuit by comparing the potential of a specific point of the call circuit section with a threshold voltage by a comparator to detect the presence of the mounting of the handset. CONSTITUTION:A handset mounting detection circuit KE1 compares the potential of a specific point whose potential is changed in response to the presence of the mounting of a handset SJ1 in a call circuit TU1, e.g., a potential VA at the point A of a resister R1 at the connector side with a threshold voltage VTH in a transmission circuit SO by a comparator CP and inputs its output to an I/O port PO1. The voltage VTH is set to an intermediate value between a potential VA1 at the point A when the handset SJ1 is mounted and the potential VA2 of the point A when the handset SJ1 is dismounted. When the voltage VTH is set in this way, the output of the comparator CP is changed attended with the change in the potential VA at the point A in response to the mounting of the handset SJ1 to the circuit section TU1 and the result is sent from the port PO1 to the processing circuit or the like.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a handset attachment detection circuit for detecting whether or not a handset (handset or headset) attached to a telephone terminal is attached to a communication circuit section. It is related to.

[Conventional technology]

FIG. 2 shows a circuit diagram of a telephone circuit section and a handset section in a conventional telephone terminal.

In FIG. 2, the telephone terminal has a telephone communication circuit section T U z
The transmitter/receiver SJz is detachably attached to the receiver using a 6-pin connector (not shown).

The telephone call circuit unit TU8 includes a transmitter circuit SO, a receiver circuit JU, and a handset attachment detection circuit K E z that detects whether or not a handset SJz is attached to the telephone call circuit unit TU.

In addition, the handset SJz has a microphone MK and a receiver R.
3 and a shorting line SH.

Microphone MK is connected to the transmitting circuit SO through two pins of the connector, receiver R3 is connected to the receiving circuit Jul through two pins of the connector, and the receiver attachment detection circuit KEt is connected to the connector MK. A short circuit line SH is connected through the 2 pins.

In the circuit consisting of the transmitting circuit SO and the microphone MK, the power supply voltage VCC is applied to the series circuit of the resistor R1 and the microphone MK, and the voltage of the microphone MK is applied to the transistor T through the series circuit of the capacitor C1 and the resistor R1.
It is added to the series circuit between the base and emitter of R and the resistor R4. A resistor R2 is connected to the collector of the transistor Tr.
and the power supply voltage V through the parallel circuit of capacitor C2.
cc has been added.

In such a configuration, the audio signal output from the microphone MK of the handset SJg is amplified by an amplifier circuit including a transistor Tr, etc., and is supplied to the next stage circuit in the telephone terminal.

In addition, the audio output from the receiving circuit JU is
It will be supplied to receiver R3 of SJZ.

Furthermore, the handset attachment detection circuit KE2 consists of a relay Ry and its contacts ry and I/○ baud) POz, and a +12V DC voltage is applied to one end of the relay Ry, and the other end of the relay Ry is connected to the handset SJ. .

I10 boat PO
For example, one input terminal of 1 is normally open type (normally closed type is also possible)
It is grounded through the contact ry.

In this handset attachment detection circuit KEt, the telephone communication circuit section TUt
On the other hand, when handset SJ is attached, relay Ry is energized, contact ry is turned on (off for normally closed type), and the input terminal of I10 boat PO1 is grounded (for normally closed type). In this case, it becomes open M), which is I10 boat PO□
The information is transmitted from the telephone terminal to a processing device (not shown) such as a CPU within the telephone terminal. On the other hand, if handset SJt is disconnected, relay Ry is not energized, contact y is off (on in the case of a normally closed type), and the input end of I10 boat PO□ is in an open state (normally closed). In the case of a closed type, it becomes a ground state a), which is I1
It is transmitted from the 0 port PO2 to the processing unit within the telephone terminal.

Therefore, this handset attachment detection circuit KE can detect whether or not the handset SJ is attached to the telephone communication circuit unit TU2, and transmit the detected information to a processing device in the telephone terminal.

The processing device that received the above signal is the handset SJ.

The operation mode of the telephone terminal is automatically switched depending on whether the telephone terminal is attached or not, or the communication circuit unit TU.

You will have to separate the

[Problem to be solved by the invention]

However, in order to detect whether or not the handset SJx is attached to the communication circuit unit TU, the handset attachment detection circuit K E 2 requires a short-circuit line S H to be provided in the communication circuit unit TU. As a connector for connecting part TU2 and handset SJt, in addition to 2 bins for transmitting and 2 bins for receiving, a total of 4 bins, there are 2 bins for connecting the shorting line SH, for a total of 6 pins. I needed something, and I couldn't use the handset SJ, which has a connector with a total of 4 bins, 2 bins for sending and 2 bins for receiving, which is used in -a, so I created a special one. There was a problem in that it was necessary to do so, resulting in high costs.

Furthermore, the handset attachment detection circuit KE2 itself uses an expensive relay Ry, which poses a problem in that the cost becomes even higher.

Therefore, an object of the present invention is to provide a handset attachment detection circuit that can detect whether or not a handset is connected to a communication circuit section without providing a circuit for detecting whether or not the handset is attached. A (Means for Solving the Problems) The transmitter/receiver 2''i attachment detection circuit of the present invention is provided to detect whether or not a transmitter/receiver is attached to a communication circuit section of a telephone terminal. It is characterized by comprising a comparator that compares the potential at a specific point, where the potential changes depending on whether the handset is attached or not, with a threshold voltage.

[For production]

In the configuration of the present invention, the potential at a specific point within the telephone terminal increases or decreases depending on whether the handset is attached to the telephone terminal or removed from the telephone circuit. When this potential is compared with a threshold voltage using a comparator, the output level of the comparator changes depending on whether the handset is attached or removed. Therefore, by monitoring the output level of the comparator, it is possible to detect whether the handset is attached to the communication circuit section.

〔Example〕

An embodiment of the present invention will be explained with reference to FIG. 1. FIG. 1 shows a circuit diagram of a telephone circuit section and a handset section in a telephone terminal according to an embodiment.

In FIG. 1, the telephone terminal has 4
The transmitter/receiver SJ+ is detachably attached to the bin via a connector (not shown).

The communication circuit unit TU is connected to the transmitting circuit SO, the receiving circuit JU, and the transmitting/receiving circuit i? It consists of a handset attachment detection circuit KE that detects whether or not the ssJ+ is attached to the speech circuit section TO, and a handset attachment detection circuit KE. KEl is different from that in FIG.

In addition, the handset SJ, the microphone MK and the receiver R
3 for general use, and does not have a short circuit line as shown in Fig. 2.

A microphone MK is connected to the sending circuit SO through two pins of the connector, and a receiver R3 is connected to the receiving circuit JtJ through two pins of the connector.

The circuit consisting of the transmitting circuit SO and the microphone MK has the same structure as that shown in FIG. 2 and operates in the same manner.

Further, the relationship between the receiving circuit JU and the receiver R3 of the handset S J + is also the same as that in FIG. 2.

Next, we will discuss the handset attachment detection circuit KE, which is the main part of the present invention.
The configuration and operation of 1 will be explained in detail.

This handset attachment detection circuit KE is a communication circuit section T U
Compare the potential vA at a point A on the connector side of the resistor R at a specific point where the potential changes depending on whether the handset SO is attached or not in the transmitter circuit SO, with a threshold voltage VTM using a comparator cp, The output of the comparator CP is input to the I10 baud) PO. In this case, the potential ■1 at the point A is applied to the positive input terminal of the comparison 2BBcp via the resistor R1, and the threshold voltage VTR is applied to the negative input terminal of the comparator CP. The threshold voltage vyx is created by dividing the power supply voltage VCC by the resistors R, , R,.

The above threshold voltage VT+1 is the potential VAI at point A when the transmitter/receiver SJ is attached and the potential VA at point A when the transmitter/receiver R35J+ is disconnected! is set to a value intermediate between

When the threshold voltage VTH is set in this way, the handset SJ,
Potential V at point A depending on whether or not the communication circuit unit TU is installed.
, the output level of the comparator cp changes with the change in . The output of this comparator CP is I10 port PO,
The data is input to the I10 boat PO, and sent to the processing circuit in the telephone terminal.

Therefore, this handset attachment detection circuit KEI detects whether or not the handset SJI is attached to the telephone communication circuit unit TU, and detects the presence or absence of the attachment of the handset SJI to the telephone communication circuit unit TU.
can be transmitted to.

The processing device that receives the above signal automatically switches the operating mode of the telephone terminal depending on whether or not the handset SJ is attached, or the communication circuit section T U +
You will have to separate the

Here, changes in the potential at point A and the threshold voltage VTH depending on whether or not the handset SJ is attached to the communication circuit section TtJ,
Transmitter S J + will be explained in more detail about the relationship between
When the microphone MK is attached, a current flows through the resistor R to the microphone MK, and the voltage VCC is divided between the resistor R1 and the microphone MK. Therefore, the potential VAI at point A at this time becomes Va+-Vcc·Rsx/(R++RHx), where R□ is the direct current resistance of microphone MK.

On the other hand, when the handset SJ is disconnected, the microphone current as described above does not flow, and the point A is in a floating state. Therefore, the potential ■4□ at point A at this time is approximately equal to the power supply voltage Vcc (> VAI).

In the comparator CP, the potential at point A is
In order to accurately detect the presence or absence of the handset SJ, by comparing the handset 'rn with the handset SJ.

It is necessary to make a sufficiently large difference between the potential ■□ when the handset SJ is attached and the potential VAt when the handset SJ is detached. For example, if the resistance values of DC resistor R1 and resistor R3 of microphone MK are set equal, the potential ■A+ at point A when handset SJ is attached becomes VAI # 'A' Vcc, and This can provide a sufficient difference compared to the potential VAt (#Vcc) at point A when SJ is removed.

Note that in the above explanation, the potential VA at point A accompanying the audio current
Although the fluctuation of T is not mentioned, the change in A with the sound current
When the potential VAI at point VAI fluctuates, the peak of potential ■□ and the potential ■ at point A when the handset SJI is disconnected. It goes without saying that there needs to be a sufficiently large difference between the two.

The handset attachment detection circuit KEI of this embodiment uses a comparator CP to detect a threshold voltage T at point A of the communication circuit TU.
, l by comparing the handset SJ.

Since the configuration is to detect whether or not the handset SJ is attached,
It is possible to detect whether the handset SJ is attached to the communication circuit unit TU without providing a circuit for detecting whether the handset SJ is attached to the communication circuit unit TU. Therefore, a general handset with a 4-pin connector can be used as the handset SJ, and costs can be reduced. Furthermore, since the presence or absence of the handset SJ is detected by the comparator CP instead of a relay as in the conventional example, the circuit can be manufactured at low cost.

In the above embodiment, the potential at point A on the connector side of resistor R is compared with the threshold voltage, but if the potential changes depending on whether or not the transmitter/receiver SJI is attached, For example, if there is such a point in the receiving circuit JU, it is possible to detect whether the handset SJ+ is attached by comparing the potential at that point with a threshold voltage.

〔Effect of the invention〕

According to the handset attachment detection circuit of the present invention, the presence or absence of the attachment of the handset is detected by comparing the potential at a specific point of the communication circuit section with a threshold voltage using a comparator. It is possible to detect whether or not the handset is attached to the communication circuit section without providing a circuit for detecting the presence or absence. Therefore, a general handset and receiver having a 4-pin connector can be used as the handset and the cost can be reduced. Furthermore, since the comparator detects whether or not the handset is attached, the circuit can be manufactured at low cost.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a telephone circuit section and a handset/receiver section in a telephone terminal according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a telephone circuit section and a handset/receiver section of a conventional telephone terminal. TU, ...Speech circuit section, SJ, ...Handset, SO.
...Talking circuit, JU...Receiving circuit, KE, ...Handset attachment detection circuit, PO, ...I10 boat, cp...
・Comparator S. Figure 2

Claims (1)

[Claims] In a handset attachment detection circuit that detects whether or not a handset is attached to a communication circuit section of a telephone terminal, a threshold voltage is defined as a potential at a specific point in the communication circuit section at which the potential changes depending on whether or not the handset is attached. A transmitter/receiver attachment detection circuit characterized by comprising a comparator for comparing.