JPS59189760A - Cordless telephone set - Google Patents

Abstract

PURPOSE:To prevent the radio interference to adjacent homes or rooms and the wiretap by performing the communication between a telephone set body and a handset with brightness-modulated infrared rays and adopting frequency division or/and wavelength division. CONSTITUTION:A circuit equipment A is provided in the telephone set body side, and a circuit equipment B is provided in the handset side. In the equipment A, a light emitting part 6 radiates brightness-modulated infrared rays. A light receiving part 7 receives brightness-modulted infrared rays radiated from the handset side and converts them to an original electric signal of modulation. A demodulating circuit 10 demodulates this modulated electric signal to convert it to a voice signal, and this voice signal is transmitted to a telephone line through a balancing network 1. In the equipment B, a receiving part of the handset receives radiated modulation infrared rays and onverts them to a voice signal to generate voice from a receiver 17, for example, a speaker. Meanwhile, voice applied to a transmitter 18, for example, a microphone is modulated by a modulating circuit 22. Since the carrier frequency is changed to f1 and f2 between the transmission from the telephone set body to the handset and the transmission from the handset to the telephone set body, bidirectional calls are secured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a cordless telephone that eliminates the cord from the telephone body to the handset.

□ Load technology and its problems Conventional cordless telephones use radio waves, so if you try to extend their range, they may cause interference with other cordless telephones used in neighboring houses or rooms. ,
Or the problem of being wiretapped.

There is. To avoid interference, it is necessary to prepare multiple frequency bands (channels), and to prevent eavesdropping, it is necessary to install a scrambling device, etc., making the system that much more complicated and expensive. Furthermore, because radio waves are used, an antenna is required, which requires operations such as extending it, making it inconvenient to handle.

Purpose of the Invention The present invention provides a cordless telephone that uses infrared rays instead of radio waves to avoid interference and eavesdropping with neighboring houses and rooms, is easy to handle, and can reach a wide range within the room. This is what I am trying to do.

SUMMARY OF THE INVENTION The present invention performs communication between a telephone main body and a handset using brightness-modulated infrared rays, and furthermore, uses frequency division (changing the carrier frequency for modulation) or wavelength division (changing the carrier frequency for modulation).
By changing the center wavelength of infrared rays) or by using this in combination, it is possible to have two-way communications and terminology where you can freely send and receive calls.

Embodiment FIG. 1 is a block diagram showing an example of an electrical system according to the first invention of the present application. In the figure, A indicates a circuit device provided on the telephone main body side, and B indicates a circuit device provided on the handset side. In A, (I) is a balanced network as in a directly operated telephone,
One end thereof is connected to a telephone terminal, and the other end is connected to a transmitter and a receiver. (2) is the audio amplifier, (3) is the modulation circuit, (4) is the RF amplifier, (5) is the band pass filter, and (6) is the light emitting part. These (2) to (6) are the main body of the phone. Take a closer look at the transmitter. (7) is the light receiving section, (8) is the band pass filter, (9) is the RF amplifier,
GO) is a demodulation circuit, (lυ is an audio amplifier, and these (9) to (1υ) constitute a receiving section in the main body of the telephone. The modulation circuit (3) is a voice amplifier that is added via the balanced circuit network (1). The gear 1J frequency f1 is modulated (FM or AM modulation, etc.) by the voice signal of the other party.In this case, the 11th frequency of the band pass filter (5) is also set to fl.The light emitting part (6) is It has a center wavelength of φ1 (e.g. 800 mm) and includes an appropriate number of infrared light emitting elements (e.g. [1)) and a circuit for lighting them, and emits infrared light whose brightness is modulated by the above modulation signal. (See Figure 4).The light receiving section (includes an optical filter with a center wavelength φ1, a light receiving element such as a photodiode, and an amplifier, and the luminance modulated light emitted from the handset side. The demodulation circuit (101 is a
This modulated electrical signal is demodulated and converted into an audio signal. This voice signal is sent to the telephone line via a balanced network (1).

Note that the bandpass filter (8) has a center frequency of +2 for reasons described later.

In B, (1) is the light receiving section, (13) is the bandpass filter, (14) is the It F amplifier, (C is the demodulation circuit, (
16) is an audio amplifier, (17) is a handset, and these (121 to (17) constitute a receiving section in the handset. ) O) is, for example, a key-shaped dial, eυ is an encoder that creates a dial signal according to the pressed key, +22) is a modulation circuit, (23) is an RF anzo, (2 gradient is a band pass filter, (251 is The light-emitting section (+8) - (251 constitutes the transmitting section in the handset. The light-receiving section (14 is the same as the light-receiving section (7) and the band-pass filter (131 is the same as the band-pass filter (5)). That's fine.

The demodulation circuit α9 may be similar to the demodulation circuit +10>, but the carrier frequency to be demodulated is fl. That is,
The receiving section of the handset receives the emitted modulated infrared rays, converts it into an audio signal, and generates audio from the handset (1'7), for example, a speaker. On the other hand, the voice applied to a transmitter (181, for example, a microphone) is modulated in a modulation circuit (221), but here the carrier frequency to be modulated is
shall be. Therefore, the center frequency of the bandpass filter (241-) is also set to +2. However, the center wavelength of the infrared rays of the IJD in the light emitting part (2
It is 1. For example, when performing iFM modulation, fl, +2
For example, 300 kHz and 700 kl (about z is appropriate.

The infrared rays emitted by the light emitting parts (6) and (2) on the telephone body side and the transmitter/receiver 4 side are emitted from the room (as shown by the arrow in Fig. 4).
If the light is reflected by the ceiling (C) etc. inside the 34J and reaches the light receiving parts (14 and The carrier frequency is fl
, +2, so two-way communication is ensured.

FIG. 2 is a block diagram showing an example of an electrical system according to the second invention of the present application. Since the basic configuration of this example is the same as that in FIG. 1, a part of the handset side B is omitted. The difference between this example and the one in FIG. 1 is that the light emitting part (6'),
(25') and the light receiving sections (12') and (7'). Therefore, only this part is marked with a dash, and the other corresponding parts are given the same reference numerals. In this example, the center wavelength of the infrared rays used for transmission from the B side to the A side is set to φ2 (for example, 90
0 M), and the modulation carrier frequency is both fl, although it is different from the center wavelength φ1 of the infrared rays used for transmission from the A side to the B side.

Therefore, the light receiving section (12') is provided with an optical filter having a center wavelength .phi.1, and the light receiving section (7') is provided with an optical filter having a center wavelength .phi.2. Even if you do this, two-way communication will not be possible with HJ.
It is Noh.

Although not shown, the frequency division method as shown in Fig. 1 and m
The fact that it is possible to combine the wavelength division method as shown in Figure 2 is as follows.
Of course.

FIG. 3 shows an example of a light receiving section that can be used in the embodiment of the present invention, (a) and Φ) are its circuit diagrams, and (C) is its frequency characteristic diagram. In the figure (a), (28) indicates a photodiode, and RL indicates a load resistance. In this circuit, due to the junction capacitance between the photodiode (28) and the load resistor RL, the input capacity of the amplifier, etc., there is a tendency for the high frequency portion to drop as shown by the three curves in FIG. (b) In the figure,
R indicates a feedback resistance. In this circuit, the feedback resistance R of the negative input amplifier increases as the load resistance, and the cutoff frequency for lowering the high frequency range increases by the gain of the amplifier, as shown by curve 6 in the diagram (C). Therefore, infrared L Pi I) and photo
A diode can be used.

FIG. 4 is a schematic diagram illustrating an embodiment of the invention.

In the figure, (3υ is the telephone body, C (2 is the handset, (281 is the photo diode, the handle is the lens, (:
301 is a plurality of (for example, 6 to 10) LEDs. If these light emitting and light receiving elements are attached to the top surface of 3υ and (3υ) and their directivity is directed upward, it will look like
, 1 can be effectively used, and the service area in the room (b) can be widened. In addition, (+
7).

(I (to), (2Q is (17) in Figure 1, fl,
This corresponds to +20+. Also, although not shown,
Needless to say, a hook switch mechanism is provided that opens the contacts when the handset C2 is hung or placed on the telephone main body 01).

Effects of the Invention Because conventional cordless telephones use radio waves, special consideration is required to prevent interference with neighboring houses or rooms, etc., or eavesdropping.
Whereas conventional antennas had poor operability, the present invention uses infrared light-emitting elements and light-receiving elements to perform multiplexing using frequency division or wavelength division, which prevents messages from leaking outside the room and prevents interference. It is possible to create a cordless telephone, which has advantages such as not requiring an antenna that is susceptible to eavesdropping and is troublesome to operate.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of an electrical system according to the first invention of the present application, FIG. 2 is a block diagram showing an example of an electrical system according to the second invention of the present application, and FIG. 3 is a light receiving section that can be used in an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating an embodiment of the present invention. Gυ...telephone body, CQ...handset, C(0)...
...Infrared light emitting element, fl, f2...Carrier frequency, (31,!2'2)...Modulation means, (2 mark...Infrared light receiving element, (1■, +15)...Demodulation means ,φ1
．． φ2...Center wavelength of infrared rays. Agent Sadado Ito Hidemori Matsukuma

Claims (1)

[Claims] (1) The telephone main body and the handset trap each include an infrared light emitting element, means for applying a signal obtained by modulating a carrier frequency with an audio signal, and an infrared light receiving element and means for demodulating its output into an audio signal. A code 4 telephone capable of making four bidirectional calls by differentiating carrier frequencies modulated in the telephone main body and the handset. 2. The telephone main body and the handset are each provided with an infrared light emitting element, means for applying a signal obtained by modulating a carrier frequency with an audio signal, and an infrared light receiving element and means for demodulating the output thereof into an audio signal; A cordless telephone that enables two-way communication by making the center wavelengths of the infrared rays of the light-emitting elements of each handset and receiver different. 3. The cordless telephone according to claim 1, wherein the center wavelengths of infrared rays of the light emitting elements in the telephone main body and the handset are different.