GB2175773A - Alarm systems - Google Patents

Abstract

An interphone system, which has a security function, includes a first talk unit (40) composed of a transmitting section (45) and an announcement section (44) and a second talk unit (1), composed of a transmitting section (2) and an announcement section (16), and in which two-way talking is possible between the first and second talk units. The announcement section (16) of the second talk unit (1) is provided with an alarm signal from an alarm generation circuit (3) through a signal attenuation circuit (60) where the alarm signal is attenuated when an environmental abnormality occurs during talking between the first (40) and second (1) talk units, thus preventing the alarm signal from being directly fed unattenuated to the announcement section (16) of the second talk unit (1). <IMAGE>

Description

SPECIFICATION Interphone system with security function The present invention relates to an interphone system composed of a master and slave interphones, and in particular, to an interphone system with security function.

Recently, interphones, enabling two-way talking between the inside of a house and its entrance or between rooms, which are equipped with a security function capable of sensing an abnormal-environment and issuing an alarm sound have come into wide use.

An example of such an interphone system with a security function is shown in Fig. 1.

An interphone system is composed of a master interphone 1 and a slave interphone 40 (hereinafter refer to as door-phone). Master interphone 1 includes a microphone 2 which is the transmitting section of a well known handset (not illustrated), and a speaker 16 which is the announcement section of the handset. Microphone 2 is connected with a constant current circuit 5 through an amplifier 3 and a hook-switch 4. Hook-switch 4 is open as illustrated when the handset is put in the rest position, and closed when the handset is taken up from the rest position. Constant current circuit 5 feeds a prescribed current to amplifier 3. The output of amplifier 3 is changed in response to the input of microphone 2. Thus, constant current circuit 5 outputs a voltage signal corresponding to changes of the output current of amplifier 3.

The output signal of constant current circuit 5 is fed to the primary coil of an impedancematching transformer 10 through a DC-cut capacitor 6, an analog switch 7, a power amplifier 8 and a DC-cut capacitor 9 in series. It is designed that the voltage obtained in the secondary coil of transformer 10 is fed to door-phone 40 described later. Further, the voltage obtained at the intermediate tap of transformer 10 is fed to a speaker 16 through a DC-cut capacitor 11, an analog switch 12, an amplifier 13, a DC-cut capacitor 14 and one of the contacts 15a of a hook-switch 15.

When putting the handset on it's rest position, one of the contacts 1 5a of hook-switch 15 closes. When taking up the handset from the rest position, the other contact 15b closes as illustrated. That is to say, a talking line is formed to make possible two-way talking with door-phone 40 by microphone 2 and speaker 16.

The output current of constant current circuit 5 is fed to a calling switch button 17 (push-button type automatic reset and normal open contact) through hook-switch 4. Then, the voltage occurring at the interconnecting point between constant current circuit 5 and hook-switch 4 is fed to the input of a call switching circuit 18 and a call-alarm sound generation circuit 30. Call switching circuit 18 includes first and second inputs 18a and 18b.

When the prescribed voltage is fed to first input 18a, analog switches 7 and 12 are set to ON and a logical "1" signal is fed to a power circuit 20 through a resistor 19. When the voltage fed from the connecting point between constant current circuit 5 and hookswitch 4 to the second input 1 8b is at zero level, analog switches 7 and 12 are to be forcibly set to OFF. Then, the voltage produced to one of the contacts 1 5a of hookswitch 15 is fed to first input 18a of call switching circuit 18.

A power circuit -20 applies the DC voltage V to resistors 21 and 22 and to the collector and emitter of an NPN type transistor 23. The output of call switching circuit 18 is applied to the base and emitter of transistor 23 through resistors 19, 24 and 25. Resistor 21 is connected in parallel to the base and emitter of a PNP transistor 26. Power circuit 20 is operated by inputting a logical "1" signal, and outputs the collector voltage of transistor 26 to the secondary coil of transformer 10 and power amplifier 8, respectively.

An environment sensing circuit 27 is composed of a contact 28 and a resistor 29 of an environmental sensor, i.e. flame sensor, gas sensor, etc., and the DC voltage V is applied to contact 28 through resistor 29. Therefore, when an abnormality, such as fire or gas-leakage, in the environment occurs, a logical "1" signal is transmitted by setting contact 28 to ON. The output of the environment sensing circuit 27 is fed to the call-alarm sound generation circuit 30. Call-alarm sound generation circuit 30 outputs a call tone signal when the voltage of input A or B is at zero level, and outputs an alarm sound signal when the output of the environment sensing circuit 27 is a logical "1". The output of call-alarm sound generation circuit 30 is fed to speaker 16 through a DC-cut capacitor 31 and the other contact 15b of the hook-switch 15.

Furthermore, the output of the call-alarm sound generation circuit 30 is fed to the input of power amplifier 8 through the DC-cut capacitor 31 and analog switch 34. The output of the environment sensing circuit 27 is fed to the input of power circuit 20 through a diode 32 in the forward direction and alarm control circuit 33. When the output of environment sensing circuit 27 is a logical "0", the alarm control circuit 33 sets the analog switch 34 to OFF and, when the output of environment sensing circuit 27 becomes a logical "1", the alarm control circuit 33 sets the analog switch 34 to ON.

The door-phone 40 is composed of a main control section 41, a resistor 42, a calling switch button 43 (push button type automatic reset and normal open contact), a speaker 44, a microphone 45, etc., and is connected to the talk line of the master interphone 1. One of the output-lines of the door-phone 40 is connected to the call-alarm sound generation circuit 30 through the talking line of the master interphone 1.

Therefore, when an abnormality in the environment occurs, the output of the environment sensing circuit 27 becomes a logical "1".

Then, the call-alarm sound generation circuit 30 generates the alarm sound signal, which is fed to speaker 16, and the door-phone 40 through the analog switch 34, power amplifier 8 and transformer 10. That is to say, the alarm sound issues from both speakers 16 and 44 of the master interphone and the door-phone 40. At the same time, the power circuit 20 operates and the alarm control circuit 33 sets the analog switch 30 to ON.

When pressing the calling switch button 43 Of the door-phone 40, the voltage of input A of the call-alarm sound generation circuit 30 in the master interphone 1 comes to zero level, and the call-alarm sound generation circuit 30 produces the calling tone signal. The calling tone signal is fed to speaker 16 through the other contact 15b of the hook-switch 15, and the speaker 16 issues calling tone.

When the user takes up the handset of the master interphone 1 in response to the calling tone, the hook-switch 4 closes, and one of the contacts 15a of the hook-switch 15 also closes. When closing contact 15a of hookswitch 15, a hook signal caused by the internal resistance of the speaker 16 is fed to the call switching circuit 18. This call switching circuit 18 sets the analog switches 7 and 12 to ON according to the hook signal, and feeds a logical "1" signal to the power circuit 20.

Thereupon, the power circuit 20 operates, and two-way talking between the master interphone 1 and the door-phone 40 becomes possible. In this case, the voice signal from the master interphone 1 is fed to the doorphone 40 through the analog switch 7, the power amplifier 8, the transformer 10, etc..

Further, it is also fed to the speaker 16 through-the analog switch 12, the power amplifier 13 and one of the contacts 15a of the hook-switch 15 from the transformer 10.

Also, the voice signal from the door-phone 40 is fed to the speaker 16 through the secondary coil of transformer 10, the analog switch 12, the amplifier 13 and one of the contacts 1 5a of the hook-switch 15.

However, in this above described system when an abnormality in the environment occurs during talking between the master interphone 1 and the door-phone 40, the alarm sound signal generated by call-alarm sound generation circuit is fed to the talking line, and issues from the speaker 6 of the master interphone 1 superimposed on the voice signal.

When this occurs, there are naturally the problems that the talking between users is interrupted and the user's ears are hurt by the excessive alarm sound.

The present invention seeks to provide an improved interphone system, which has a security function enabling the issuance of an alarm sound without hurting the user's ears and without disruptively interfering with the talking in the event that an abnormality in the environment occurs during a conversation.

According to the present invention there is provided an interphone system with a function comprising: (A) a first talk unit having a transmitting section and an announcement section; and (B) a second talk unit enabling a two-way talking with the first talk unit, said second talk unit including, (1) a handset component having a transmitting section and an announcement section, (2) an environment sensing means for outputting a sensing signal in response to an environmental change, (3) an alarm generation means for respectively feeding an alarm signal to the announcement sections of the first and second talk units on the basis of the sensing signal from the environment sensing means, and (4) a signal attenuation means for feeding the alarm signal to the announcement section of the second talk unit after attenuating the alarm signal when the alarm signal is output from the alarm generation means during talking between the first and second talk units.

Preferably the system includes an alarm control circuit to interrupt the alarm signal fed to the first talk unit, when the sensing signal is output from the environment sensing circuit during talking.

For a better understanding of the present invention reference will now be made, by way of example, to the accompanying drawings, wherein like reference numerals throughout the various Figures denote like structure elements and wherein: Figure 1 shows a circuit example of an interphone system; Figure 2 shows a circuit of an embodiment of an interphone system with a security function according to the present invention; and Figure 3 shows an example of an alarm control circuit used to the circuit in Fig. 2.

Hereinafter, an embodiment of the present invention will be described with reference to Figs. 2 and 3 of the drawings. However, as mentioned, in the drawings, the same reference numerals are used to denote the same element, and therefore a detailed description of the elements which are common with Fig.

1 will not be repeated.

As shown in Fig. 2, an alarm control circuit 50 is provided in place of the alarm control circuit 33 shown in Fig. 1. The output of environment sensing circuit 27 and a voltage obtained from the contact 15a of the hookswitch 15 are both fed to the alarm control circuit 50. An AC coupling capacitor 60 as signal attenuation means is connected in parallel with the hook-switch 15.

The alarm control circuit 50 is constructed as shown in Fig. 3. A signal S1 from the environment sensing circuit 27 is fed to one of the inputs 51 a of AND circuit 51, and a signal S2 from the hook-switch 15 is fed to the other input 51b of the AND circuit 51 through a low pass filter 52. The low pass filter 52 passes a hook signal fed from the hook-switch 15, but eliminates a voice signal.

The output of the AND circuit 51 is fed to the analog switch 34, and when the output of the AND circuit 51 is a logical "0", the analog switch 34 is ON and when the output of the AND circuit 51 becomes a logical "1", the analog switch 34 turns OFF. A DC voltage V is applied through a pull-up resistor 53 to the input of the low pass filter 52.

The operation of the above-described arrangement will now be described.

When an abnormal situation, e.g. fire etc., occurs, the output of the environment sensing circuit 27 becomes a logical "1" and then, the call-alarm sound generation circuit 30 produces the alarm sound signal, and the power circuit 20 operates. At this time, since the contact 15a of the hook-switch 15 is in the OFF-state, no hook signal is produced and, therefore, the alarm control circuit 50 sets the analog switch 34 to ON. The alarm sound signal is directly fed to speaker 16, and also fed to the door-phone 40 through the analog switch 34, the power amplifier 8 and the transformer 10. That is to say, the alarm sound issues from both speakers 16 and 44 of the master interphone 1 and the doorphone 40.

When the calling switch button 43 in the door-phone 40 is pressed, the voltage of input A of the call-alarm sound generation circuit 30 in the master interphone 1 is at zero level, and the call-alarm generation circuit 30 produces a calling tone signal. The calling tone signal is fed to speaker 16 through the contact 15b of the hook-switch 15, and as a result, speaker 16 issues a calling tone. When the user takes up the handset of the master interphone 1 in response to the calling tone, the hook-switch 4 closes, and the contact 15a of the hook-switch 15 also closes. Therefore, a hook signal caused by the internal resistance of the speaker 16 is fed to call switching circuit 18. In response to the hook signal, the call switching circuit 18 sets the analog switches 7 and 12 to ON and feeds a logical "1" signal to the power circuit 20.

Then, the power circuit 20 operates, and twoway talking between the master interphone 1 and the door-phone 40 becomes possible. In this case, the voice signal in the master interphone 1 is fed to the door-phone 40 through the analog switch 7, the power amplifier 8 and the transformer 10. Further, this voice signal is also fed to the speaker 16 through the other contact of the analog switch 12, the power amplifier 13 and the hook-switch 15 from the transformer 10. Also, the voice sig nal from the door-phone 40 is fed to the speaker 16 through the secondary coil of the transformer 10, the analog switch 12, the amplifier 13 and the contact 1 5a of the hookswitch 15. During talking between the master interphone 1 and the door-phone 40, the hook signal is also fed to the alarm control circuit 50.

In this condition, when an abnormal situation in the environment occurs, the AND circuit 51 in the alarm control circuit 50 produces a logical "1" output signal when a "1" is outputted from the environment sensing circuit 27, and the analog switch 34 is set to OFF. Therefore, even though the alarm sound signal is generated from the call-alarm sound generation circuit 30, it is not fed to the talking line. That is to say, the alarm sound signal directly supplied to the talking line is interrupted. After attenuation by capacitor 60, the alarm sound signal is fed to the speaker 16 through contact 15 of the hook-switch 15 and thus an attenuated alarm sound issues from speaker 16.

Therefore, the alarm sound can securely issue without hurting the ears of the handset user and without interrupting the talking.

In summary, it will be seen that the present invention overcomes the disadvantages of the prior art and provides an improved interphone system with security function which can issue an alarm sound without hurting the user's ears when an environmental abnormality occurs during talking.

Claims (6)

1. An interphone system with a function comprising: (A) a first talk unit having a transmitting section and an announcement section; and (B) a second talk unit enabling a two-way talking with the first talk unit, said second talk unit including, (1) an handset component having a transmitting section and an announcement section, (2) an environment sensing means for outputting a sensing signal in response to an environmental change, (3) an alarm generation means for respectively feeding an alarm signal to the announcement sections of the first and second talk units on the basis of the sensing signal from the environment sensing means, and (4) a signal attenuation means for feeding the alarm signal to the announcement section of the second talk unit after attenuating the alarm signal when the alarm signal is output from the alarm generation means during talking between the first and second talk units.

2. An interphone system with security function according to claim 1, further including an alarm control means for interrupting the alarm signal which is fed to the first talk unit from the alarm generation means when the sensing signal is output from the environment sensing means during talking between the first and second talk units.

3. An interphone system with security function according to claim 2, wherein said first talk unit includes a calling switch.

4. An interphone system with security function according to claim 3, wherein said alarm generation means includes a calling tone generation means for outputting a calling tone when the calling switch is operated.

5. An interphone system with security function according to claim 4, wherein said second talk unit includes a hook-switch for feeding a hook signal indicating a talking state to the alarm control means in association with the handset component thereof.

6. An interphone system substantially as hereinbefore described with reference to Figs.

2 and 3 of the accompanying drawings.