JPS5857830A - Input circuit for fm carrier interphone - Google Patents

Abstract

PURPOSE:To obtain an input circuit of transformerless type, by using a filter employing a piezoelectric material. CONSTITUTION:A four-terminal construction piezoelectric filter 4 is used, in which input terminals 5a, 5b and output terminals 6a, 6b are isolated from each other so as not to have a common surface conduction pattern (shown in hatched lines). The input terminals 5a, 5b of the filter 4 are connected to a commercial AC line 7 and output terminals 6a, 6b are connected to an amplifier 8. This filter can pick up an FM signal from the line 7 and separate an AC 100V, allowing to eliminate a transformer 1 which had been needed for conventional systems and to simplify the constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an input circuit for a transformerless FM carrier intercom using a four-terminal piezoelectric r-wave device.

An FM carrier intercom uses a commercial AC line already installed inside a building and transmits and receives FM-modulated audio signals on it.If you have a fee, you can plug this intercom into it. It is an extremely simple device that allows you to make calls immediately with just a single touch. As mentioned above, this intercom uses a commercial AC line (100V
Since the FM signal is carried by a 5 dHz or 60 Hz electric light, the input circuit needs to have two functions: to separate the AC so that 100 V voltage does not flow into the system, and to pick up only the carrier wave. be.

According to the prior art, as shown in FIG.
AC separation of 00V is performed by a transformer 1, and a three-terminal piezoelectric f-wave device 2 extracts only the carrier wave and sends it to an amplifier. There is also a method of arranging a capacitor in place of the piezoelectric f-wave device and configuring an LC tuned circuit with the L of the transformer and C of the capacitor to extract the carrier wave, but due to poor selectivity, in many cases the former piezoelectric r A configuration using a wave device is adopted.

In any case, according to the conventional technology, an input voltage transformer is indispensable, so the structure is complicated, the cost is high, a lot of space is required for parts, and installation on a printed circuit board is troublesome. was there.

SUMMARY OF THE INVENTION An object of the present invention is to provide an FM carrier intercom input circuit having a completely new circuit configuration that can overcome the drawbacks of the prior art.

In order to achieve such an object, the present invention provides a P-wave device using piezoelectric material with a four-terminal structure in which the input and output are separated,
This is a transformerless input circuit, and this is precisely the feature of the present invention.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 2 is an input circuit diagram of the FM carrier type intercom according to the present invention. An R-wave device 4 using a piezoelectric material has a four-terminal structure in which its input terminals 5a, 5b and output terminals 6a, 6b are insulated and separated so that their surface conductive patterns are not common. The input terminals 5 a and 5 b are connected to the logical AC line 1 and the output terminals 6 g and 6 b are connected to the amplifier 8 .

As a concrete structure of the piezoelectric r-wave device, for example, as shown in FIG. 3, two vibrators 10&.

Each vibrating piece 10a is a so-called H-type vibrator in which tabs are connected and integrated by a connecting piece 11 at the center thereof.

There is one in which conductive patterns (indicated by diagonal lines) are provided on the front and back surfaces of each +ob, and one side is connected to the input side and the other side is connected to the output side.

In addition, as shown in FIG. 4, two
An R-wave device using a longitudinal vibration mode may also be used, in which conductive patterns (indicated by diagonal lines) are separately provided, and conductive patterns (contours are indicated by broken lines) are placed on the back surface at positions corresponding to those on the front surface. In addition, although not shown in the drawings, an R-wave device using a spreading mode may be used.

In any case, with such a configuration, the necessary signal (carrier signal) can be extracted from the commercial AC line, and the AC 100V can be completely separated. It goes without saying that the K and R wave generators are manufactured so that the 6F1 wave characteristics match the signal frequency to be extracted. Thus, according to the present invention, the r-wave device can serve both AC separation and P-wave functions.

Since the present invention is configured as described above, the transformer that was previously indispensable is not required, wiring can be easily done on the printed circuit board, the footprint can be reduced, and only one small piezoelectric element is required as a component, so the space is reduced. It has excellent effects, such as being able to significantly lower the electrical resistance, and since it is a piezoelectric plate, it has extremely good electrical insulation and is safe even if a short circuit occurs in the system.

[Brief explanation of the drawing]

Figure 1 is a conventional circuit diagram, Figure 2 is a circuit diagram of the present invention, and Figure 3 is a conventional circuit diagram.
FIG. 4 is an explanatory diagram showing an embodiment of a piezoelectric f-wave device, respectively. 4-... Original R wave device, 5a, 5b... Input terminal, 5a
, 6b...Output terminal, 1...Commercial AC line, 8...
amplifier. Patent Applicant Fuji Electrochemical Co., Ltd. Agent Yuki Omata Shiima
Shigemi Tanema Araki
Tomonosuke 1 figure 112 figure 11F3 figure

Claims (1)

[Claims] 1. An R-wave device using a piezoelectric material is made into a four-terminal structure with its input terminal and output terminal electrically insulated and separated, and the input terminal is connected to a commercial AC line and the output terminal is connected to an amplifier. This is an input circuit for an FM carrier type intercom that combines two AC separation and f-wave functions.