JP2005295425A - Line delivery level controlling circuit and communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a line delivery level controlling circuit capable of preventing transmission signal distortion even if a voltage at a public line side drops to narrow a sound dynamic range in a power interruption supporting telephone equipment. <P>SOLUTION: The line delivery level controlling circuit is equipped with a switch circuit 2 for closing and liking at the time of off hook to transmit and receive transmission and reception signals to the public line and deliver dial pulses, a hybrid circuit 3 and a telephone equipment controlling circuit 6 that separate the reception signals and the transmission signals from each other and adjust a direct current resistive value and an alternative impedance, an electric source switching circuit 5 for performing electric power supply to the telephone equipment controlling circuit 6 at the time of the power interruption by switching to a voltage of the public line, and further a gain adjustment amplifier 65 for varying an amplification degree of the transmission signal in quantity depending on the voltage of the public line detected by a voltage detection circuit 64 for detecting the voltage of the public line. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention, for example, in a communication device such as a power failure-compatible telephone capable of making a call even in the event of a power failure, controls the transmission level to the line according to the level of the line voltage at the time of the call and eliminates the distortion of the transmitted voice. The present invention relates to a level control circuit.

  Since the public line itself functions as a DC power supply, the telephone basically does not need a separate power supply and is not affected by a power failure. However, multi-function telephones such as push phones, answering machines, and facsimiles in recent years use a commercial power source as a main power source for operating those functions. When the commercial power source is used as the main power source in this way, the telephone cannot be used during a power failure.

  Therefore, in Patent Document 1, when the main power supply is energized, it is exchanged with an external line via a line transformer in the main device, and when the main power supply is interrupted, it is directly connected to the external line without going through the line transformer. A power failure detection relay that operates normally to selectively form an energized call loop that is used when the main power supply including the common call circuit is energized and an uninterrupted call loop that is used when the main power source is interrupted Between the contact, the first and second diodes inserted in series into the current call loop and the call loop during power outage to prevent the loop current from wrapping around each other, and the rectified output terminal inserted into the call loop during power outage A diode bridge connected to the communication circuit via the second diode, and a common line side rectified output terminal of the diode bridge and a line side of the first diode. Power failure for telephone circuits key telephone apparatus provided with a capacitor connected, and a resistor as a column is disclosed.

  However, in the power failure telephone circuit disclosed in Patent Document 1, it is necessary to form a power call loop and a power failure call loop separately, and another circuit is required to generate a power failure power supply. There is a problem that the configuration becomes complicated and the number of parts increases and the cost increases.

  Therefore, the present inventor has devised a power generation circuit for a telephone with a power failure call function as shown in FIG. FIG. 3 is a circuit diagram showing the power generation circuit, and a diode bridge 1 connected to two lines of a connector inserted into a modular jack from a public line, and a switch circuit which closes when off-hook and sends a dial pulse. 2, a hybrid circuit 3 that separates a received signal and a transmitted signal, a power source switching circuit 5 that switches between a power source during energization and a power source during a power failure, and a telephone control circuit 6. The telephone control circuit 6 supplies a dial pulse and a switch-on signal to the switch circuit 2 and also stores a CPU 61 for controlling the telephone and a RAM (Random for storing the operation program of the telephone and temporarily storing the processing of the CPU 61. A memory 62 including an access memory (ROM) and a read only memory (ROM), and a signal processing circuit 63 that processes the received signal and the transmitted signal and supplies the processed signal to a transmitter / receiver (not shown).

  The diode bridge 1 forms a full-wave rectifier circuit and is provided so as to always supply a current in a fixed direction to the telephone circuit regardless of the polarity of the public line on the exchange side.

  The switch circuit 2 is a circuit for receiving a reception signal from the public line and transmitting a dial pulse or a transmission signal to the public line, and is composed of transistors Tr1 and Tr2 and resistors R1 to R4. Yes. The transistor Tr2 is a transistor that is turned on / off by a dial pulse signal from the CPU 61, and is turned on during a call to turn on the transistor Tr1.

  The hybrid circuit 3 has a function of adjusting a direct current resistance value and an alternating current impedance value in addition to a function of separating a reception signal and a transmission signal.

  The voltage switching circuit 5 uses a terminal voltage of a constant voltage diode ZD1 connected between the resistor R9 of the hybrid circuit 3 and the ground. The voltage switching circuit 5 is connected in one direction from the smoothing capacitor C1 to the telephone control circuit 6 from the main power source. A voltage for driving an IC or a digital circuit constituting the telephone control circuit 6 includes a first diode D1 for supplying a voltage and a second diode D2 for supplying a voltage from the capacitor C1 to the telephone control circuit 6 in one direction. (2.2V) is supplied.

  In this power generation circuit, power is normally supplied from the power source such as an AC adapter to the telephone control circuit 7 via the first diode D1, but the voltage on the anode side of the first diode D1 disappears during a power failure. Therefore, the first diode D1 is turned off. On the other hand, the constant voltage diode ZD1 provided on the ground side of the hybrid circuit 3 generates a predetermined voltage by the voltage from the public line. Power is supplied to the telephone control circuit 6 via the diode D2.

Thereby, the DC voltage generated in the hybrid circuit 3 can be used as a power source during a power failure.
JP 63-258193 A

  In the circuit of FIG. 3, the dynamic range of sound is determined by the voltage between the power supply line of the hybrid circuit 3 and the terminal of the constant voltage diode ZD1.

  On the other hand, there is a regulation concerning the current supply in the telephone office switchboard, “The circuit current when the two lines are terminated with a pure resistance of 300Ω is 15 mA or more, and when terminated with a pure resistance of 50Ω, it is 130 mA or less. It has become.

  The amount of current actually supplied from the station side to the telephone side varies within this specified range depending on the equipment and distance of the station to which the telephone is connected.

  For this reason, in a telephone designed with a DC resistance value of 300Ω, when a current of 20 mA is supplied from the station side, the line voltage becomes 6V, and thereby the voltage drop (about 1.6V) due to the diode bridge 1 and the transistor Tr1. The voltage (2.2V) obtained by subtracting the terminal voltage (about 2.2V) of the constant voltage diode ZD1 from the line voltage is not a problem as the dynamic range of the voice, but the line voltage is higher than this depending on the distance of the connected stations. If it decreases, the dynamic range of the sound becomes narrower.

  When the voice dynamic range is narrowed, if the voice input to the hybrid circuit 3 is large, it is clipped and distorted, and when this is sent to the outside line as a transmission signal, the voice becomes hard to hear.

  Accordingly, the present invention provides a line transmission level control circuit and a communication apparatus that can prevent distortion of a transmission signal even when the voltage on the public line side at the time of a power failure decreases and the voice dynamic range becomes narrow. Objective.

The present invention is provided with a voltage detection circuit for detecting the voltage of the public line during a call, and provided with a gain adjusting means for increasing or decreasing the amplification degree of the transmission signal according to the voltage of the public line detected by the voltage detection circuit. Main features.

  The present invention relates to a voltage detection circuit that detects a voltage of a public line in a communication device that can operate by power supply from the public line even in the event of a power failure, and to transmit speech according to the voltage of the public line detected by the voltage detection circuit Since gain adjustment means to increase / decrease the signal amplification level is provided, even if the voltage on the public line drops due to the equipment and distance of the station to which the telephone is connected and the voice dynamic range becomes narrow, distortion of the transmitted signal is reduced. There is an advantage that it can be prevented.

  The present invention is designed to prevent distortion of a transmission signal even when the voltage on the public line side decreases due to the equipment and distance of a station to which a communication device (for example, a telephone) is connected and the dynamic range becomes narrow. For this purpose, a voltage detection circuit for detecting the voltage of the public line during a call is provided, and a gain adjusting means for increasing or decreasing the amplification degree of the transmission signal according to the voltage of the public line detected by the voltage detection circuit is provided. It was realized.

  A first invention made to solve the above problems is a switch circuit which is closed when a device is off-hook and transmits / receives a transmission / reception signal to / from a public line, and transmits a dial pulse, and a reception signal and a transmission signal And a hybrid circuit that adjusts the DC resistance value and AC impedance value seen from the exchange side, and a control circuit that performs various control of the equipment, and the power supply to the control circuit at the time of power failure is made the voltage of the public line A line transmission level control circuit in a communication apparatus (for example, a telephone) that is switched, a voltage detection circuit that detects a voltage of a public line, and a transmission signal of a transmission signal according to the voltage of the public line detected by the voltage detection circuit Gain adjusting means for increasing or decreasing the amplification degree is provided.

  In the first aspect of the invention, the voltage on the public line side decreases due to the equipment and distance of the station to which this communication apparatus is connected, so that the dynamic range of the transmitted voice is narrowed, and distortion occurs when a loud sound is input. In order to prevent this, the amplification factor of the amplifier that amplifies the transmission signal is automatically increased or decreased according to the voltage of the public line. As a result, the distortion of the sound transmitted from the apparatus is eliminated, and the other party can easily hear. In the present invention, it is not essential to adjust the dynamic range of the received signal. The reason for this is that the received signal is attenuated to some extent by the resistance of the public line, and it is not necessary to adjust the gain, and the other party's telephone also has a gain adjusting means for preventing distortion of the transmitted signal. This is because if it is provided, it is not necessary to take a means for taking distortion in both.

  According to a second aspect of the present invention, there is provided a power supply switching circuit comprising: a first diode that supplies a voltage in one direction from a main power supply to a control circuit; and a constant circuit connected to a ground side of the hybrid circuit. It is composed of a second diode for supplying a voltage in one direction from the voltage diode to the telephone control circuit.

(Embodiment 1)
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIG. 1 and FIG.

  FIG. 1 is a circuit diagram showing a power generation circuit according to Embodiment 1 of the present invention, which is connected to a diode bridge 1 connected to two wires of a connector to be inserted into a modular jack from a public line and closed when off-hook. A switch circuit 2 for transmitting a dial pulse, a hybrid circuit 3 for separating a received signal and a transmitted signal, a power source switching circuit 5 for switching between a power source during energization and a power source during a power failure, a telephone control circuit 6, and voltage detection A resistive voltage divider 7.

  The telephone control circuit 6 supplies a dial pulse and a switch-on signal to the switch circuit 2 and also stores a CPU 61 for controlling the telephone and a RAM (Random for storing the operation program of the telephone and temporarily storing the processing of the CPU 61. A memory 62 composed of an access memory (ROM) and a read only memory (ROM), a signal processing circuit 63 that processes the received signal and the transmitted signal and gives them to a handset (not shown), and a resistance component composed of resistors R10 and R11. A voltage detection circuit 64 that detects the voltage of the public line based on the voltage divided by the pressure device 7, a transmission signal gain adjustment amplifier 65, and a reception signal gain adjustment amplifier 66 is provided.

  The diode bridge 1 forms a full-wave rectifier circuit and is provided so as to always supply a current in a fixed direction to the telephone circuit regardless of the polarity of the public line on the exchange side.

  The switch circuit 2 is a circuit for receiving a reception signal from the public line and transmitting a dial pulse or a transmission signal to the public line, and is composed of transistors Tr1 and Tr2 and resistors R1 to R4. Yes. The transistor Tr2 is a transistor that is turned on / off by a dial pulse signal from the CPU 61, and is turned on during a call to turn on the transistor Tr1.

  The hybrid circuit 3 forms a DC resistance value and an AC impedance value in addition to the function of separating the received signal and the transmitted signal.

  The DC resistance value of the telephone is specified. “The DC resistance value when the DC circuit is closed (when the handset is raised) is measured at a current of 20 mA to 120 mA, except when a dial signal is sent. It should be 50Ω or more and 300Ω or less (however, there are exceptions depending on the type of switch). Further, the switching system entrance viewed from the subscriber side has a balanced series impedance of 600Ω and 1 μF, and in order to match this, the terminal side needs to be designed to have a balanced 600Ω AC impedance.

  The voltage switching circuit 5 uses a terminal voltage of a constant voltage diode ZD1 connected between the resistor R9 of the hybrid circuit 3 and the ground. The voltage switching circuit 5 is connected in one direction from the smoothing capacitor C1 to the telephone control circuit 6 from the main power source. A voltage for driving an IC or a digital circuit constituting the telephone control circuit 6 includes a first diode D1 for supplying a voltage and a second diode D2 for supplying a voltage from the capacitor C1 to the telephone control circuit 6 in one direction. (2.2V) is supplied.

  In this power generation circuit, power is normally supplied from the power source such as an AC adapter to the telephone control circuit 6 via the first diode D1, but the voltage on the anode side of the first diode D1 disappears during a power failure. Therefore, the first diode D1 is turned off. Since a predetermined voltage is generated by the voltage from the public line in the constant voltage diode ZD1 provided on the ground side of the hybrid circuit 3, the second diode D2 is used by using the voltage smoothed by the capacitor C1. Power is supplied to the telephone control circuit 6 via

  During a call, the CPU 61 detects a power failure, and the voltage detection circuit 64 detects the voltage on the public line side based on the voltage at the output terminal of the diode bridge 1. Since the voltage on the public line side fluctuates depending on the impedance inside the line or the telephone, the amplification level of the transmission signal gain adjustment amplifier 65 is adjusted according to the voltage value, and the transmission signal is determined by the voice dynamic range in the hybrid circuit 3. Do not saturate. FIG. 2 shows a procedure for gain adjustment in the CPU 61.

In FIG. 2, in step S1, it is monitored whether or not the line is closed. When the line is closed, the line voltage is checked in step S2. Next, in step S3, a gain corresponding to the line voltage is set in the transmission signal gain adjustment amplifier 65.

  Thereby, even if the voice dynamic range is lowered, it is possible to prevent the voice of the transmission from being distorted and becoming difficult to hear on the other party's telephone.

In FIG. 1, the amplification level of the received signal is also adjusted by the received signal gain adjusting amplifier 66, but this is not essential. The reason is that the received signal is attenuated to some extent by the resistance of the public line, and there is no need to adjust the gain, and the other party's telephone also has a gain adjusting means for preventing distortion in the transmitted signal. This is because if it is provided, it is not necessary to take a means for taking distortion in both.
In the above description, the line transmission level control circuit according to the present invention is applied to a telephone. However, the circuit may be applied to a facsimile apparatus having a telephone function.

  The present invention relates to a communication device capable of operating by power supply from a public line even in the event of a power failure, and a line in which transmission voice distortion is controlled by controlling a transmission level to the line according to the level of the line voltage at the time of the power failure The transmission level control circuit can be used in the field of telephones.

1 is a circuit diagram showing a power generation circuit according to Embodiment 1 of the present invention. The flowchart which shows operation | movement of CPU in Embodiment 1 of this invention. Schematic diagram showing the power generation circuit invented earlier

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diode bridge 2 Switch circuit 3 Hybrid circuit 5 Power supply switching circuit 6 Telephone control circuit 7 Resistance voltage divider 61 CPU
62 memory 63 signal processing circuit 64 voltage detection circuit 65 transmission signal gain adjustment amplifier 66 reception signal gain adjustment amplifier D1 first diode D2 second diode ZD1 constant voltage diode

Claims (3)

The switch circuit that closes when off-hook and transmits / receives the transmission / reception signal to / from the public line, and transmits the dial pulse, and separates the reception signal and the transmission signal, and the DC resistance value and AC impedance as seen from the switch side Line transmission in a communication apparatus provided with a hybrid circuit that adjusts values, a control circuit that performs various control of devices, and a power supply switching circuit that switches power supply to the control circuit during a power failure by switching to the voltage of the public line A level control circuit,
A line transmission comprising: a voltage detection circuit for detecting a voltage of the public line; and a gain adjusting means for increasing or decreasing the amplification degree of the transmission signal in accordance with the voltage of the public line detected by the voltage detection circuit. Level control circuit. The power supply switching circuit supplies a voltage to the control circuit in one direction from a first diode that supplies a voltage from the main power supply to the control circuit in one direction, and a constant voltage diode connected to the ground side of the hybrid circuit. 3. The line transmission level control circuit according to claim 2, comprising a second diode. The switch circuit that closes when off-hook and transmits / receives the transmission / reception signal to / from the public line, and transmits the dial pulse, and separates the reception signal and the transmission signal, and the DC resistance value and AC impedance as seen from the switch side A hybrid circuit that adjusts the value, a control circuit that performs various controls of the device, and a power supply switching circuit that switches the power supply to the control circuit during a power failure to the voltage of the public line,
A voltage detection circuit for detecting a voltage of the public line;
A communication apparatus comprising: gain adjusting means for increasing / decreasing the amplification degree of the transmission signal according to the voltage of the public line detected by the voltage detection circuit.

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