KR920001435B1 - Hook-off detecting circuit - Google Patents

Abstract

The method detects on-off states of hook not influenced by bouncing of hook switch. The method comprises: (A) detecting the bouncing of a hook switch peridically by checking the present contact state and former contact state of the hook switch and (B) discriminating the on-off state of the hook switch when debouncing state is maintained for a fixed time. The duration of a constant debouncing state is checked by counting the number of the constant debouncing state detection.

Description

Hook on-off detection method in telephone

1 is a circuit diagram of a hook on-off detection circuit using a mechanical contact switch.

2 is an operational waveform diagram for FIG.

3 is a circuit diagram of a hook on-off detection circuit using a magnetic switch.

4 is a flow chart according to the present invention.

The present invention relates to a method for detecting a hook on-off state in a telephone.

In general, a telephone is a type of communication terminal that provides a voice call between subscribers by connecting to an exchange system. The telephone is an analog type telephone that provides only a voice call by an analog signal, and a voice call and various information services by a digital signal. There is a digital phone that can provide.

Unlike conventional analog telephones, the digital telephones maintain the transmission line always in a closed circuit regardless of the hook on-off state, so that the digital telephone should be frequently transmitted and received with the switching system. Detect on-off status and send digital message about hook on-off status to exchange system.

In the digital telephone, the conventional hook on-off detection circuit includes a CPU (Central Processing Unit) 10 for controlling the peripheral circuit of the telephone as shown in FIG. 1, and the operation of the CPU 10. FIG. The CPU 11 stores a program, a RAM 12 for temporarily storing information processed by the CPU 10, and a detachable state of a handset (not shown). It consists of a mechanical contact switch SW as a hook switch to inform (10), and a resistor R1 for pulling up the output of the mechanical contact switch SW to a power supply voltage Vcc.

The hook on-off detection circuit of FIG. 1 is connected to a mechanical contact switch (SW) used as a hook switch and is changed by on-off switching of the mechanical contact switch (SW) in accordance with the detachment state of the handset to the CPU 10. The CPU 10 was examined for the logic state on the line 1 to be detected, and the hook on-off state was detected.

In the configuration of FIG. 1, the mechanical contact switch SW has a bouncing period T in which the logic state is unstable for a predetermined time as shown in FIG. 2 when the handset is attached or detached, so that the CPU 10 is in a hook on-off state. There was a problem that could be misrecognized.

As a result, the CPU 10, the ROM 11, the RAM 12, the magnetic switch MSW, and the permanent magnet are shown in FIG. 3 to reduce the bounce period as described above. A hook on-off detection circuit composed of (13) and fall-up resistor R1 has been used.

The configuration circuit of FIG. 3 is configured by replacing the mechanical contact switch SW of the configuration circuit of FIG. 1 with the magnetic switch MSW and installing a permanent magnet 13 in the handset. The CPU 10 and the ROM 11 ), The ram 12 and the pull-up resistor r1 are the same and the reference numerals are the same.

In the configuration of FIG. 3, the CPU 10 controls a peripheral circuit by a program stored in the ROM 11, processes data transmitted and received, and checks a hook on-off state by checking a logic state on the line 1. . The RAM 12 temporarily stores the data processed by the CPU 10. In addition, the permanent magnet 13 moves up and down according to the detached state of the handset to turn on or off the magnetic switch (MSW) used as a hook switch. Then, the magnetic switch MSW is turned on by the magnetic force of the permanent magnet 13 to maintain a low logic state on the line 1, while off the magnetic field, and is turned off to maintain a high logic state on the line 1. Let's do it.

As described above, in the hook on-off detection circuit of FIG. 3, the magnetic switch MSW is operated by a magnetizing force, so that the bounce period T is shorter than that of the mechanical contact switch SW of FIG. Allow CPU 10 to more accurately detect hook on-off conditions.

However, since the bouncing period T still exists when the magnetic switch MSW is switched, the CPU 10 may incorrectly recognize the hook on-off state.

Accordingly, an object of the present invention is to provide a hook on-off detection method capable of accurately detecting a hook on-off state without being affected by bouncing of a hook switch in a telephone.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The circuit for carrying out the invention is the same as the circuit diagram of FIG. 1 or FIG. 3 described above, and the same reference numerals.

4 is a flow chart according to the present invention, which detects the bounce contact state by checking the current contact state and the previous contact state of the hook switch at regular intervals, and the bouncing contact state. When the bounce contact state detected in the detection process (30-31, 37) is constant, the hook-on state of the hook switch is counted by counting the number of bounce contact state detections up to a predetermined number and being maintained for a predetermined time. The hook state determination process (32-36, 38-42) is determined.

Hereinafter, an operation example of FIG. 3 according to the present invention will be described in detail with reference to FIGS. 1 to 3.

First, the hook on-off detection performed on the telephone according to the flowchart of FIG. 3 according to the present invention is performed in the hook on-off detection circuit using the mechanical contact switch of FIG. 1 or the hook on-off detection circuit using the magnetic switch of FIG. Although it can apply, it demonstrates, for example, when applying to the structural circuit of FIG.

The CPU 10 of FIG. 3 executes the program of FIG. 4 whenever an interrupt occurs at a constant cycle. When an interrupt occurs, the magnetic switch MSW used as a hook switch is checked in step 30 by checking the logic state on the line 1. ) To determine if it is on.

If the magnetic switch (MSW) whose logic state on the line (1) is a low logic state in step (30) is on, the CPU 10 sets the hook state flag assigned to a register in itself in step (31) to " 1 ". Check if it is set and if the previous state was hook on.

In the state (31), if the hook state flag is determined to be the hook off state other than "1", the CPU 10 checks whether the count value of the counter built in itself is a certain number in step (32).

Here, the predetermined number is set to, for example, 15 as a preset value for detecting the hook-off state only when the on state of the magnetic switch MSW is maintained for a predetermined time or more.

When the count value is a predetermined number (eg, 15) in step 32, the CPU 10 initializes the counter value to “0” in step 33, and then proceeds to step 34 to set the hook state flag to “1”. Set to "."

After performing step (34), the CPU 10 transmits a message on the hook on state to the switching system through the peripheral circuit and the transmission line in step 35, and then returns to the main program.

The peripheral circuit for transmitting the hook-on message is not shown in the drawings because it is a known fact in the general configuration of a digital telephone. When the counter value of the counter is not a predetermined number (eg, 15) in step (32), the CPU 10 adds “1” to the count value in step 36 and returns to the main program.

On the other hand, when the magnetic switch (MSW) whose logic state on the line (1) is a high logic state in step (30) is off, the CPU 10 sets the hook state flag built into itself in step (37) to "0". Check if it is reset to determine if the previous state was hooked off.

If the hook state flag is not "0" in the hook off state in step (37), the CPU 10 checks whether the count value of the counter built in itself is a certain number in step (38). Here, the predetermined number is set to, for example, 15 as a value that is set in advance to detect the hook-on state only when the off state of the magnetic switch MSW is maintained for a predetermined time or more.

If the count value of the counter is not a predetermined number (for example, 15) in step (38), the CPU 10 adds “1” to the count value of the counter in step 39 and then returns to the main program. .

If the count value of the counter is a predetermined number (eg, 15) in step (38), the CPU 10 initializes the count value of the counter to “0” in step (40), and then proceeds to step (41). The hook status flag is reset to " 0 " to indicate the hook off status.

After performing step (41), the CPU 10 transmits a message about the hook-off state to the switching system through the peripheral circuit and the transmission line in step 42 and then returns to the main program.

If the hook state flag is "1" in step (31) and the whole state is hook on, or in step (37), if the hook state plug is "0" and all state is hook off, the CPU 10 returns to the main program. Go back. Steps 30, 31, and 37 of the flowchart are for detecting parts equal to 21 or parts equal to 20 within the bouncing period T in the second diagram.

The part consisting of the steps from (32) to (36) and the part consisting of the steps from (38) to (41) determine the hook on state and the hook off state by counting the bounce contact times. It is to. The interrupt period is about 2 ms and the bounce period T in the second diagram is about 30 ms, and a certain number, which is the limit of the number of bounce contacts, that is, the count value of the CPU 10, is a value obtained by dividing the bounce period T by the interrupt period. Is set to 15.

On the other hand, as described above, an example in which the present invention is applied to the hook on-off detection circuit using the magnetic switch of FIG. 3 has been described. However, switching according to detachment of the handset is performed by hook on-off using the mechanical contact switch of FIG. It will be appreciated that the same can be applied to the present invention because it is the same in the detection circuit.

As described above, the present invention has the advantage of detecting the correct hook on-off state by counting the number of debounced contact states of the hook switch and determining the hook on-off state by the state maintained for a predetermined time. .

Claims (1)

Hook on-off of a digital telephone having a CPU 10 for controlling the peripheral circuits of the telephone and a hook switch for switching the handset's detached state to inform the CPU 10 of the detached state of the handset. A detection method comprising: a bounce contact state detection step of detecting a bounce contact state by inspecting a current contact state and a previous contact state of the hook switch at regular intervals, and the bounce contact state detected in the bounce contact state detection process is constant Hook on-off detection, comprising: a hook state determination process of determining the on-off state of the hook switch by counting the number of bounce contact state detections up to a predetermined number of times Way.

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