JPS6227885Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a speaker line abnormality detection circuit, and is used in cases where the distance between the amplifier and the speaker is long (some tens of meters to more than 1 km), such as in river discharge alarm systems. The present invention relates to a line abnormality detection circuit.

Conventionally, in this type of speaker system, the method of confirming whether the speaker is operating normally is to amplify the signal for inspection from the oscillator 1 with the amplifier 2, as shown in FIG.
A constant level output is supplied to the speaker line, and the current value induced in the detection coil 5 at this time is measured by a level meter 6 to detect abnormalities in the speaker line including the speaker. However, with the method shown in Figure 1, although it is possible to determine the presence or absence of an abnormality when one or two speakers are connected to an amplifier, it becomes extremely difficult to determine the presence or absence of an abnormality when several or more speakers are connected. . Furthermore, since fluctuations in the amplifier output are usually considered due to fluctuations in the power supply voltage and changes in temperature, there is a drawback in that accurate signal determination cannot be made when these fluctuations are taken into consideration.

In order to eliminate such drawbacks, the present invention switches between a reference pseudo load and a speaker load on the output side of the amplifier, detects the load current in each case, and compares the difference between the two. This is to determine whether there is an abnormality in the speaker line including the speakers, and will be explained in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention, in which an oscillator 1, an amplifier 2, a matching transformer 3, a speaker load 4, a detection coil 5, and a level meter 6 correspond to those in FIG. A rectifier, 9 a DC amplifier, and S a switch.

Now, in Fig. 2, if we turn the switch S to the pseudo load 7 side and apply the signal from the oscillator 1 to the amplifier 2, we get
A current is induced in the detection coil 5. This current is rectified by a rectifier 8, amplified by a DC amplifier 9, and a level meter 6
Compare the indicated value of the level meter 6 when the power is supplied to the speaker load 4 with the indicated value of the level meter 6 obtained in the same way as the pseudo load 7 by moving the switch S to the side of the speaker load 4. This is to determine whether there is a short circuit or disconnection.

Accurate impedance adjustment between the speaker load 4 and the pseudo load can be detected accurately if the impedance is adjusted in advance using the rectifier 8 or the DC amplifier 9.

As explained above, if this circuit is used, even if the output is affected by power supply voltage fluctuations or temperature changes, or if several speakers are connected in parallel to one amplifier, the speaker It is possible to reliably determine abnormalities in the speaker line, including abnormalities in the speaker line.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional speaker line abnormality detection circuit, and FIG. 2 is a block diagram of a speaker line abnormality detection circuit showing an embodiment of the present invention. 1... Oscillator, 2... Amplifier, 3... Matching transformer, 4... Speaker load, 5... Detection coil,
6... Level meter, 7... Pseudo load, 8... Rectifier, 9... DC amplifier, S... Switch.

Claims (1)

[Scope of utility model registration request] In a speaker line abnormality detection circuit that applies a test signal to a speaker line to be tested and detects a current due to the test signal to determine whether the speaker line to be tested is good or bad, a pseudo load equivalent to the speaker line and a A speaker line abnormality detection circuit comprising a pseudo load and a switch for switching and feeding the test signal to the speaker line, and detecting an abnormality in the speaker line by comparing respective detected currents. .