The present invention relates to an intelligent alarm apparatus with interfacing to a telephone network, comprising of a sensor, signal detector, processor, and interfacing to a switched telephone network.

The basic object of the invention to achieve an alarm apparatus with interfacing to a telephone network using such a novel type of circuit technology in the apparatus that allows an alarm message originating from an alarm sensor to be transmitted via a telephone network without the need for a local power supply.

Different kinds of alarm sensors are currently in use offering a connection to an alarm system, from where the alarm is further routed to the telephone network by means of an automatic calling unit.

Prior art sensors require interfacing at a low impedance level. The alarm message is routed in the form of a current signal to an alarm system control unit. Several sensors may be attached to the control unit, each at a separate input. Further, the supply voltage to the sensors is provided by the alarm system power supply.

The control unit of the alarm system transfers a detected alarm to an automatic calling unit, which subsequently transmits the alarm to an alarm control point.

In a conventional system, the alarm control unit requires a power supply and backup battery. In addition, the automatic calling unit requires a separate power supply with a backup battery. The batteries must be dimensioned so as to have a

sufficient capacity even when the current loads of sensor loops are included. For minimized disturbance, the loop current levels are typically in the order of 5...10 mA. Consequently, small systems requiring only one sensor would be excessively complicated and costly to build.

Furthermore, the battery life is limited, and so a battery malfunction causes the majority of faults in alarm equipment.

The object of the invention is to achieve an alarm apparatus, which replaces an alarm control unit and an automatic calling unit, yet still providing equivalent functions. The particular object of the invention is to achieve an alarm sensor which is directly interfaceable to the telephone network without the need for a local power supply and backup battery.

This object of the invention is achieved by what is stated in the characterizing parts of the claims.

In accordance with the invention, only one alarm sensor of low current consumption is used, which is mounted in the same encapsulation with a processor and is attached directly, without the use of an alarm control unit, to the interrupt input of the processor. In its standby state, the processor is set to a power-saving state called the "wait" mode. It is not until an interrupt is generated that the procedure for alarm transmission (equally as with an automatic calling unit) to the alarm control point is initiated.

The supply voltage is produced from the telephone network, which may be loaded up to 1 mA max. according to regulations concerning the construction of telephone networks.

This low level of current consumption is obtained by the aforementioned high-impedance sensor circuitry and by holding the processor in the standby, or the "wait" mode.

Moreover, programmed data is stored in an EEPROM type memory, whose supply voltages are switched on only for a read or write operation. Additionally, the entire circuit configura¬ tion is designed using low-power components of conventional technology.

The standby condition time is additionally utilized for charging the "storage" capacitor of the alarm apparatus, which supplies energy during an alarm condition of the apparatus.

In the following, an embodiment of the invention is described in reference to the attached drawings, in which:

Figure 1 shows the block diagram of an intelligent alarm apparatus according to the invention and

Figure 2 shows the circuit diagram of the same alarm apparatus, with the processor being shown in a simplified form.

The major units of the apparatus are an infra-red sensor 1, an integrator 2, a detector 3, and a processor 4, as well as a power supply section 5 with storage capacitors 7 (marked as C3 and C4 in Fig. 2) .

The infra-red sensor 1 is attached to an operational ampli¬ fier, configured as an integrator 2, in order to make the circuit tolerant to slow changes in the sensed environment. The time constant related to the rate-of-change is determined by elements Cl and R2. When the variations in,the sensed environment have a low rate-of-change, such as that of the room temperature, Cl is being charged making an equal voltage to be applied to the inverting and noninverting inputs of the operational amplifier so that the operational amplifier output is held to the "zero" level.

During quick variations in the sensed environment that exceed the time constant formed by Cl and R2, the operational amplifier output produces a fast pulse, which charges C2. The circuit configuration of C2, R6, and Nl forms a detector, which extends the detected pulse and generates an interrupt for the processor 4.

In the standby mode the processor is held in the low-power "wait" state, starting the call procedure at the onset of an interrupt. The processor incorporates a program, which is capable of routing the alarm via a telephone line 6 either to a private telephone number, alarm control center, and/or a paging device. The alarm routing operation is handled using routines of the conventional technology making their descrip¬ tion unnecessary in this context.

The supply voltage of the circuitry is delivered by a feed bridge SI and constant-current generators TR1 and TR2, together with storage capacitors C3 and C4. The storage capacitors used are high-capacitance value capacitors of the so-called energy-storing type super capacitors, which are charged at a constant current of 1 mA via constant-current generators TR1 and TR2 from a telephone line 6. The capaci¬ tors C3 and C4 operate as backup power sources during number dialling or short-term breaks of telephone line connections.