GB2097223A

GB2097223A - Central control systems

Info

Publication number: GB2097223A
Application number: GB8137938A
Authority: GB
Original assignee: TECNOENERGIA Srl
Current assignee: TECNOENERGIA Srl
Priority date: 1981-03-27
Filing date: 1981-12-16
Publication date: 1982-10-27
Also published as: GB2097223B; IT8167427A0; AT378305B; ATA393881A; IT1143459B

Abstract

A system is provided for centrally controlling the working of a plurality of items of equipment and plant each installed in respective premises (5) provided with telephones (7) connected to a telephone system (3). A local control unit (2) is associated with each controlled item of equipment or plant and linked to sensors (5) delivering signals indicative of the value of quantities or parameters being controlled. A central control unit (1) is connected to the local control unit (2) by telephone lines (8) extending to the telephones (7). The unit (1) delivers periodic and sequential enquiry signals to the units (2) via the lines (8). More specifically, the central unit (1) is operative to send periodically, through the telephone system (3), a first and then a second electrical call signal to the telephone (7) connected with each local control unit (2). The second electrical call signal follows the first one after a predetermined period of time (T1) longer than the time interval occurring between two normal consecutive telephone call signals. Each local control unit (2) has a sorting device (10) which is parallel connected to the telephone line (8) of the associated telephone (7) and operative to: a) parallel connect the unit (2) to the line (8) when the sorting device (10) receives two call signals spaced by an interval of time equal to (T1) in order to allow the transmission of the information signals from the unit (2) to the central unit (1) through the telephone system (3); and b) break off the connection between the unit (2) and the associated telephone line (8) once said transmission is over. <IMAGE>

Description

SPECIFICATION Central control systems This invention relates to systems for centrally controlling the working of a plurality of items or' plant disposed in different, spaced apart places.

It is known for systems of the above kind to comprise: -a plurality of electrical sensors associated with each controlled item of equipment or plant, each sensor being capable of delivering at an output thereof electrical information signals indicative of the value of an associated quantity or parameter which is being controlled; a plurality of local or 'peripheral' control units each associated with a respective one of the controlled items of equipment or plant and linked to the sensors thereof, each of the local control units being capable of receiving the electrical signals delivered by the sensors and of transmitting the signals in accordance with pre-established criteria when the local control unit receives electrical enquiry singals; and -a central control unit connected to the plurality of local control units by means of a corresponding number of communication lines and capable of sending out periodic and sequential said enquiry signals via said lines to the local control units and of receiving said information signals that the local control units transmit.

Systems of the above kind can be used, for example, for centrally controlling the working of a plurality of items of heating equipment or plant installed in premises in a small- or average-sized town centre, or in all the premises of an area or quarter of a city. In such an application, the control systems make it possible to achieve satisfactory running of the heating equipment or plant with regard to both reducing in fuel consumption and cutting down on the number of staff needed to take charge of the control and operation of the plant. The manufacture and installation of such control systems is, however, somewhat expensive because of the large number of communication lines that are necessary to connect the central contol unit to the local control units.

In order to solve this problem, it has been proposed thatzhen possible--the telephone lines of an ordinary telephone system be used as the communication lines. According to this proposal a suitable telephone transceiver, connected to a telephone line shunted from the telephone system, is installed at each local control unit. Such a solution is, however, not yet completely satisfactory and not economically advantageous.

According to the present invention there is provided a system for centrally controlling the working of a plurality of items of equipment or plant installed in respective different, spaced apart premises each provided with at least one telephone set connected to a telephone system, the system comprising:: a plurality of electrical sensors associated with each controlled item of equipment or plant, each sensor being capable of delivering at an output thereof electrical information signals indicative of the value of an associated quantity or parameter which is being controlled; a plurality of local control units each associated with a respective one of the controlled items of equipment or plant and linked to the sensors thereof, each of the local control units being capable of receiving the electrical signals delivered by the sensors and of transmitting the signals in accordance with pre-established criteria when the local control unit receives electrical enquiry signals; and a central control unit connected to the plurality of local control units by means of a corresponding number of communication lines and capable of sending out periodic and sequential said enquiry signals via said lines to the local control units and of receiving said information signals that the local control units transmit; wherein:: each local control unit can be parallel connected to a said communication line in the form of a telephone line extending to the telephone set housed in the premises which also house the associated controlled item of equipment or plant; the central control unit comprises an input/output circuit connected to the telephone system and operative periodically to send through the telephone system a first and a second electrical call signal to the telephone set associated with each local control unit, the second electrical call signal following the first electrical call signal after a predetermined period of time which is longer than the time interval occurring between two consecutive telephone call signals; and each local control unit is provided with a sorting device which is parallel connected to the telephone line of the associated telephone set and operative to carry out the following operations: (a) parallel connect the local control unit to the telephone line when the sorting device receives two call signals spaced by an interval of time substantially corresponding to said predetermined period of time in order to allow the transmission of the above-mentioned information signals from the local control unit to the central control unit through the telephone system; and (b) break off the connection between the local control unit and the associated telephone line when said transmission is over.

A control system embodying the present invention and described hereinbelow makes it possible to make use as communication lin esHf telephone lines belonging to a conventional, pre-existing telephone system, whereby it is not necessary to provide each local control unit with an additional telephone set.

The invention will now be further described, by way of illustrative and non-limiting example, with reference to the accompanying drawing, the sole figure of which is a partly block circuit diagram of a central control system embodying the invention.

The illustrated control system embodying the invention comprises a central control unit 1 and a plurality of local or 'peripheral' control units 2. The central control unit 1 is linked to a telephone system 3, for example a public switched telephone network, by means of at least one telephone line 4.

Each local control unit 2 is associated with a respective controlled item of equipment or plant (not shown). To each of these items of equipment or plant there are linked a plurality of electric sensors 5, which are connected to the associated local control unit 2 and operative to transmit to the local control unit electrical information signals indicative of the sensed values of respective quantities or parameters which are being controlled. Such quantities or parameters may be of various kinds, for example temperature, the level of a liquid in a container, the pressure inside a pipe, and so forth.

Each controlled item of equipment or plant, as well as the local control unit 2 and sensors 5 linked thereto, is housed inside a building or premises 6 provided with at least one telephone set 7 for private use, the telephone set being connected by a telephone line 8 to the telephone system 3. Each local control unit 2 is parallel connected to its respective telephone line 8 by means of a two-wire line 9.

A respective sorting or discriminating device 10 is parallel connected to each of the telephone lines 8. Each sorting device 10 comprises a call signals repeater 11 having an output connected to a timer 1 2. An output of the timer 1 2 is linked to an input of an enabling device 1 3 which is connected to a gate-controlled switch 14 capable of disconnecting the line 9 which links the local control unit 2 to telephone system 3. The call signals repeater 11 also is connected to a driving input of the gate-controlled switch 14.

Each telephone set 7 comprises a telephone transceiver for private use, which was present in the premises 6 prior to the installation of the control system. The telephone set 7 can be used in normal manner for making or receiving telephone calls to or from any other telephone connected to the system 3.

The central control unit 1 comprises an input/output circuit that is operative, according to techniques known in themselves, to delivery periodically, through the telephone system 3, a first and a second electrical call signal to the telephone set 7, connected to each local control unit 2. These signals act as 'enquiry' signals and are spaced by a predetermined period to time T1 which is longer than the time interval T between two normal consecutive call signals. This allows the sort ing device 10 associated with each telephone set 7 to detect (in the manner described hereinafter) whether a certain sequence of electrical call signals reaching the associated telephone set 7 originates from the central control unit 1 or from another telephone set (for private use) connected to the telephone system 3.In the latter case, the sorting device 10 remains inoperative and interferes in no way with the communication which may be established between the telephone set 7 and the telephone set from which the call has been made. In the former case the sorting device 10, as will be described hereinafter, connects the local control unit 2--by means of the gate-controlled switch 14 to the central control unit 1 through the telephone system 3. Once this connection has been established, the local control unit 2 transmits to the central control unit 1 the information signals provided by the sensors 5 linked to the relevant controlled item of equipment or plant.

When this transmission is over, the local control unit 2 brings about switching of the gatecontrolled device 14 and, as a consequence thereof, the connection between the local control unit 2 and the central control unit 1 is again interrupted.

The working of the illustrated system will now be described in detail.

Whenever a call pulse signal reaches a telephone line 8, the associated call signals repeater 11 repeats this signal at the input of the timer 1 2. The timer 1 2 delivers a driving signal with a pre-established delay with respect to the moment when each repeated call signal received by the device 11 ceases. Such delay may be, for instance, in the region of 10 seconds. The delayed driving signal delivered by the timer 1 2 activates the enabling circuit 1 3 to deliver an enabling signal which is supplied to an enabling input of the switch 14.

The reception of a first call pulse on the line 8 may be followed by either of the following alternatives.

I) the subsequent call pulse is delivered (with respect to the first pulse) with a delay longer that the interval between two normal consecutive telephone call pulses; or II) the subsequent call pulse is delivered with a delay substantially corresponding to the interval of time usually present between two consecutive telephone call pulses.

In the first case, the sorting device 10 'interprets' the first call pulse it receives as a call pulse originating from the central unit 1.

As soon as the second call pulse is received, the repeater 11 switches the gate-controlled switch 14. The corresponding local control unit 2 is therefore connected to the central control unit 1 thorugh the associated line 9, the telephone system 3 and the telephone line 4. The local control unit 2 transmits to the central control unit 1 the information signals provided by the sensors 5 linked thereto.

After this transmission, the local control unit 2 causes breaking of the contacts of the gatecontrolled switch 14, interrupting the connection with the central control unit 1.

The second of the two above-mentioned alternatives occurs whenever a telephone set 7 is being called by another telephone connected to the system 3. When this happens, the enabling device 1 3 does not supply an enabling signal to the gate-controlled switch 14 and, accordingly, the switch 14 stays in the state in which no connection is established between the local control unit 2 and the central control unit 1.

As mentioned above, each telephone set 7 comprises a telephone set for private use housed in the same premises 6 where a controlled item of equipment or plant is installed. It should be noted that the connection of a local control unit 2 and a sorting device 10 to such telephone set 7 does not involve any serious limitation on the use of the telephone set by the subscriber. In this connection, each local control unit 2 does not take more than 10 seconds to transmit information signals to the central control unit 1.

Each time the central control unit 1 transmits a pair of call signals to one of the telephone sets 7, the first signal makes the telephone bell ring. The subsequent call signal likewise makes the bell ring, but after a delay with respect to the first ring or set of rings considerably longer than the interval of time usually elapsing between two consecutive rings or sets of rings of an ordinary call. This enables the user of the telephone set 7 to discriminate between normal calls and those originating from the central control unit 1 and intended for the local control unit 2 connected to the telephone set 7. However, the pair of rings of the bell associated with each telephone 7 that occur each time the central control unit 1 originates a call could be a nuisance to the users of the telephone sets.

This inconvenience can be avoided, for instance, by disconnecting the bell with which each telephone set 7 is provided and by supplying each telephone set 7 with a supplementary bell 1 5. In this way, when the telephone set 7 receives a call from another telephone connected to the system 3, the supplementary bell 1 5 is activated by the timer 12, starting from the second call pulse received . In the case of a call originating from the central control unit 1, the supplementary bell 1 5 is not activated.

The sorting device 1 0 may be embodied in various different ways. According to a first embodiment, the repeater 11 can comprise a relay and the timer 1 2 and the enabling circuit 1 3 may each comprise a timed relay, while the gate-controlled switch 14 may also comprise a relay provided with a self-latching winding, that is to say a winding that closes a contact set and continues to keep it closed even if the power is turned off. It is instead possible to employ solid-state switches and electronic timers in the construction of the devices 11 to 14. Finally, it is possible to construct the whole sorting device 10 by employing some of the circuits constituting a microprocessor.

Each local control unit 2 may comprise comparators of conventional kind connected to the sensors 5 and capable of detecting anomalous variations, if any, in the signals the sensors provide at their outputs. Each local control unit 2 may in this case be provided with a device operative to dial the number of a telephone linked to a processing unit installed at the central control unit 1 whenever an information signal displays an anomalous variation. After a connection with the telephone linked to the processing unit has been established, the local control unit 2 transmits to the processing unit all the instantaneous values of the signals the sensors 5 deliver at their outputs. These signals, after reaching the processing unit, are decoded and displayed for instance by means of a printer. An operator can then inspect the printed data and trigger a warning signal, if need be, or act appropriately upon the item of equipment or plant signalling an anomalous variation in one or more controlled parameters.

Claims

1. A system for centrally controlling the working of a plurality of items of equipment or plant installed in respective different, spaced apart premises each provided with at least one telephone set connected to a telephone system, the system comprising.

a plurality of electrical sensors associated with each controlled item of equipment or plant, each sensor being capable of delivering at an output thereof electrical information signals indicative of the value of an associated quantity or parameter which is being controlled; a plurality of local control units each associated with a respective one of the controlled items of equipment or plant and linked to the sensors thereof, each of the local control units being capable of receiving the electrical signals delivered by the sensors and of transmitting the signals in accordance with pre-established criteria when the local control unit receives electrical enquiry signals; and a central control unit connected to the plurality of local control units by means of a corresponding number of communication lines and capable of sending out periodic and sequential said enquiry signals via said lines to the local control units and of receiving said information signals that the local control units transmit; wherein:: each local control unit can be parallel connected to a said communication line in the form of a telephone line extending to the telephone set housed in the premises which also house the associated controlled item of equipment or plant; the central control unit comprises an in put/output circuit connected to the telephone system and operative periodically to send through the telephone system a first and a second electrical call signal to the telephone set associated with each local control unit, the second electrical call signal following the first electrical call signal after a predetermined period of time which is longer than the time interval occurring between two consecutive telephone call signals; and each local control unit is provided with a sorting device which is parallel connected to the telephone line of the associated telephone set and operative to carry out the following operations: (a) parallel connect the local control unit to the telephone line when the sorting device receives two call signals spaced by an interval of time substantially corresponding to said predetermined period of time in order to allow the transmission of the above-mentioned information signals from the local control unit to the central control unit through the telephone system; and (b) break off the connection between the local control unit and the associated telephone line when said transmission is over.

2. A control system according to claim 1, wherein each of the sorting devices comprises: a call signal repeater parallel connected to the telephone line extending to the associated telephone set; a timer connected to an output of the repeater and arranged to be activated by the repeater in order to deliver at an output thereof a driving signal with a pre-established delay equal to said predetermined period of time each time a call signal ceases; an enabling circuit connected to the timer and operative to deliver an enabling signal on an output thereof upon receiving said driving signal; and a controlled switch provided with an enabling input connected to said output of the enabling circuit and a driving input connected to an output of the repeater, the arrangement being such that each local control unit can be linked to the telephone line of the associated telephone set by means of the controlled switch, the switch being operative to link the local control unit to the telephone line when an enabling and a driving signal are simultaneously applied to said enabling and driving inputs, respectively.

3. A control system according to claim 2, wherein a bell of each telephone set is disconnected and each telephone set has connected thereto a respective supplementary bell connected also the the associated timer.

4. A control system according to claim 2 or claim 3, wherein each call signal repeater comprises a relay.

5. A control system according to claim 4, wherein the timer and the enabling circuit each comprise a timed relay.

6. A control system according to claim 5, wherein the controlled switch comprises a relay having a self-latching winding.

7. A control system according to claim 2 or claim 3, wherein the sorting device is constituted by a microprocessor.

8. A control system substantially as herein described with reference to the accompanying drawings.