JPH084774Y2 - Ringer detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is directed to a system in which a terminal such as a facsimile is connected to a communication line such as a public telephone line via a modem and receives a charging pulse signal from the communication line. The present invention relates to an applied ringer detection device.

[Prior Art] Generally, a telephone and a terminal connected via a modem are selectively connected to a communication line via a switching device (relay circuit etc.), and a detection circuit for detecting a ringer signal is output from the switching device. Is also located on the phone side. However, it is conceivable to arrange the ringer detection circuit closer to the communication line side than the switcher in order to share circuit components. In this case, of course, the ringer detection circuit will enter the line of the modem. The ringer detection circuit is provided with, for example, a Zener diode as a constant voltage means for determining the ringer detection voltage.

[Problems to be solved by the invention] However, in the circuit configuration in which the ringer detection circuit is inserted in the line to which the modem is connected as described above, the charging pulse signal transmitted from the communication line (for example, 16 KHz burst signal) Since the charging pulse signal has a relatively high voltage level, the charging pulse signal may cause the Zener diode to operate in the Zener region when a positive voltage is applied, resulting in distortion of the charging pulse signal. Then, this distortion is output as a fluctuation of the offset for direct current (DC) to the active filter output for removing the charging pulse signal provided in the subsequent stage (in front of the modem), and as a result, the performance of the modem is improved. Will be lowered.

The present invention solves the above problems, and in a system that receives a charging pulse signal from a communication line, if a ringer detection circuit is inserted in the circuit of a modem to share parts, the charging pulse signal is It is therefore an object of the present invention to provide a ringer detection device capable of preventing the ringer detection circuit from being inadvertently operated to distort the signal and reduce the performance of the modem.

[Means for Solving the Problems] In order to achieve the above object, the present invention is a ringer detection device applied to a system in which a terminal is connected to a communication line via a modem and receives a charging pulse signal from the communication line. There, a detection circuit for detecting the ringer signal is arranged in the line to which the modem is connected, and the charging pulse signal applied to the diode is attenuated in parallel with the zener diode for determining the ringer detection voltage in the detection circuit. It is connected with a capacitor.

[Operation] In the above configuration, the charging pulse signal applied to the Zener diode is attenuated by the presence of the capacitor, the applied voltage becomes the level of the inoperative region below the Zener voltage, and the distortion of the charging pulse signal is suppressed, and therefore the modem As a result, the offset of DC component does not occur.

[Embodiment] An embodiment of the Ringer detection device of the present invention will be described below with reference to FIG.

In the figure, a telephone line (line) is connected to the terminals TIP and RING, and a ringer detection circuit RD for detecting a ringer signal transmitted from the line is connected between these terminals, and further, a relay circuit RL and a transformer. , Filter circuit F
The modem M is connected via. Also, the relay circuit
A telephone (Tel) is connected to the other side of the RL. A facsimile and a computer are connected behind the modem M.

The ringer detection circuit RD includes a capacitor C2 for AC coupling through which a ringer signal is passed, a resistor R1, a diode D1, and a series circuit of zener diodes ZD1 and ZD2 for determining ringer detection voltage connected in series in opposite directions, and a diode D1. Photocoupler PC1 connected in parallel and resistor R2 connected in parallel to the circuit of diode D1 and zener diodes ZD1 and ZD2.
In particular, in the present invention, the capacitor C1 is connected in parallel with the resistor R2. The ringer detection circuit RD operates by detecting a ringer signal having a relatively low frequency, for example, 100 Hz or less. On the other hand, the charging signal is a burst signal of 16 KHz which is a relatively high frequency.

In the above circuit, the charging signal applied to the Zener diodes ZD1 and ZD2 when the charging signal is applied is attenuated due to the presence of the capacitor C1, and the applied voltage becomes an inactive region below the Zener voltage. Therefore, the generation of distortion in the charging signal is suppressed. Therefore, the performance of the modem M when the charging signal is applied is not adversely affected. On the other hand, if the capacitor C1 is not present, the charging signal is a voltage higher than the Zener voltage, so the ringer detection circuit RD
Operates and the charging signal is distorted, which adversely affects the performance of the modem M.

Further, since the ringer detection circuit RD can be placed in front of the circuit of the modem M, the parts can be shared with other circuits. That is, the AC coupling capacitor C2 can also have the function of the capacitor of the snubber circuit in the pulse dial circuit (not shown).

It should be noted that the present invention is not limited to the configuration of the above-described embodiment, and various modifications are possible, and instead of the Zener diode for determining the Ringer detection voltage, another circuit element having an equivalent action can be used. The Zener diode described in (1) includes such a diode.

[Advantage of the Invention] As described above, according to the present invention, the ringer detection circuit is arranged in front of the modem circuit, and the circuit component of the ringer detection circuit is shared with the component of the snubber circuit of the pulse dial circuit, for example. You can In addition, since the capacitor is connected in parallel with the Zener diode for determining the ringer detection voltage, the charging signal applied to the Zener diode when the charging signal is applied is attenuated, and the applied voltage becomes an inoperative region below the Zener voltage, and the charging It is possible to prevent the signal from being distorted, so that the performance of the modem when the charging signal is applied can be maintained.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a ringer detecting device according to an embodiment of the present invention. RD ... Ringer detection circuit, ZD1, ZD2 ... Zener diode, C1 ... Capacitor, M ... Modem.

Claims (1)

[Scope of utility model registration request] 1. A ringer detection device applied to a system in which a terminal is connected to a communication line via a modem and receives a charging pulse signal from the communication line, wherein the detection circuit for detecting the ringer signal is connected to the modem. A ringer detection device, wherein the ringer detection device is arranged in the same line, and a capacitor for attenuating a charging pulse signal applied to the diode is connected in parallel with the zener diode for determining the ringer detection voltage in the detection circuit.