WO1991001539A1

WO1991001539A1 - Integrated slow scan and alarm system

Info

Publication number: WO1991001539A1
Application number: PCT/EP1989/001294
Authority: WO
Inventors: Jan Derek Parish
Original assignee: Siemens Aktiengesellschaft; Siemens Plc
Priority date: 1989-07-17
Filing date: 1989-10-30
Publication date: 1991-02-07
Also published as: EP0483140A1; DE68921079D1; EP0483140B1; DE68921079T2; AU4513189A; ATE118286T1

Abstract

An integrated slow scan and alarm system is disclosed, wherein event and picture information is stored in a transmitter unit along with an associated time reference. Alarm events can, as dictated by configuration, be made to cause the storage of one or more pictures in a digital memory. The picture source is selected with an integral video switch (7). Once a significant event has been encountered a preconfigured telephone number is dialled. A receiver unit, on answering the call, requests the transfer of the event data from the transmitter unit via the telephone connection now established. The time reference is also transferred and both this and the associated event displayed to a system operator via a standard video monitor (39).

Description

Integrated slow scan and alarm system

The present invention relates to a system integrating the func¬ tions of remote alarm communication, video picture storage and slow scan picture transmission.

Slow scan television techniques have been used in security applications to confirm the reports provided by conventional alarm detectors and possibly identify the. cause of an alarm when a remote site is being monitored over a low bandwidth channel. Remote alarm communicators provide useful additional information and facilities using similar low bandwidth channels. Numerous common circuit elements can be identified between each system. Using alarms to trigger picture storage vastly increases the possibility of determining the cause of an alarm.

Remote alarm communicators were developped to enable the moni¬ toring of alarm detection devices using widely available, low cost, low bandwidth communication channels. Systems have been developped that provide adequate monitoring of alarm situations but do not give an accurate timed record of the sequence of events at the protected premisis. In addition when it has been required in the past to implement a remote alarm facility in¬ corporating a slow scan capability it has been necessary to utilise separate equipments for the two functions or use a slow scan system with limited alarm capability. Further, develop¬ ments of slow scan systems have traditionally concentrated on achieving improvements in picture quality and transmission times rather than ensuring useful picture content and ease of operation.

Such slow scan systems are described in GB-A-1567660 or GB-A-2201563. The object or the present invention is to provide a remote alarm facility incorporating an integral slow scan function thereby giving improved corrolation between alarm events and the associated picture.

A further object is to improve and extend the remote alarm reporting to cover numerous other events associated with the remote system.

A further object is to provide accurate chronological record of the events at the remote site and to provide this without the need for an absolute time reference at each remote site.

A further object is to provide a system that can cope with a wide variety of users needs through the use of a flexible and easily accessible configuration structure.

A further object is to provide a system that can be used in mobile applications without the need for a wired connection.

The above named objects of the invention are achieved by a system as defined above, in the introduction of this text.

Event and picture information is stored in a transmitter unit along with an associated time reference. As dictated by system configuration, the stored information can be either ignored if the events are defined as insignificant, or communicated if an event is defined as significant. Particular types of events, known as alarm events, can, as dictated by configuration, be made to cause the storage of one or more pictures in a digital memory. The picture source is selected with an integral video switch. Once a significant event has been encountered a pre¬ configured telephone number is dialled. The telephone connection can be made by normal wired means or for mobile applications via radio or other non-wired technique (eg. Cellnet (Cellular Network) or radio telephone). A receiver unit, on answering the call, requests the transfer of the event data from the transmitter unit via the telephone connection now established. The time reference is also transferred and both this and the associated event displayed to a system operator via a standard video monitor. If the receiver detects that pictures have been stored at the transmitter this is signalled to the operator. Pictures are transferred on request over the same communication channel as used for event information. Once transferred both event and picture information is stored at the receiver unit. User specific configuration data is held in electrically eraseable none volatile memory. Configuration changes can be made using the same communication channel as used for event information.

According to the invention there is provided integrated slow scan alarm apparatus comprising two individual units, one dedicated to the function of event and slow scan storage and transmission and the other to the function of event and slow reception and display.

Normally the transmission unit will include a means for video input switching allowing the selection of one of a number of video sources. The unit may also include a method of video signal digitisation control such that the video signal range is matched to that of the memory storage means. The unit may also include a video sync detection means to inform the micropro¬ cessor controlling means of the condition of the selected video source.

Further the unit may also include a means for allowing the microprocessor controlling means to request the storage of a frame of video information in the memory storage means .

Normally the unit will provide a mode of operation allowing the signals presented on the alarm input means to cause the storage of a frame of video information. The unit may also include a queueing means such that alarms or other events detected by the unit are stored in chronological order. In addition the unit may also include a timing means such that the relative time of the alarms or events stored by the queueing means are stored alongside the associated alarm or event. Normally the receiver unit will provide a method of user con¬ trol allowing selection of various displays of event and slow scan information sent from the transmitter unit via the low bandwidth channel. The unit may also include a serial communi- cation interface providing listed output of all stored events at the transmitter unit. Additionally the unit may provide an interface to a P.C. to enable the local and remote upload and download of transmitter and receiver configuration details.

The invention will be more closely described in the following with reference to embodiments which are shown in the drawings in which

fig. 1 is a schematic block diagram of a transmitter unit fig. 2 is a schematic block diagram of a receiver unit and fig. 3 is a schematic block diagram of a mobile application of the system.

The system essentially consists of two matching equipments, a transmitter unit capable of accepting alarm and video informa¬ tion and sending this via a dial up telephone connection to a receiver unit for subsequent display and logging. In the pre¬ ferred embodiment the receiver unit can have up to twenty asso- ciated transmitter units, only one of which may be connected at a time.

In the transmitter (fig. 1) a microprocessor control and coor¬ dination subsystem (1) handles all the decision, monitoring and communication aspects of the unit. Alarms are interfaced via the conditioning and protection circuit (2) to the alarm multi¬ plexer (3). Alarm scanning is performed under the control of the microprocessor (1) whereby each alarm is selected in turn and monitored using the alarm window comparator (4). The status of each alarm is stored and also displayed if dictated by con¬ figuration details. A separate alarm conditioning and protec¬ tion circuit (5) and window comparator (6) is used for the special alarm "Tamper", whenever an intruder tries to destroy the system, its alarm sensors or wiring. If dictated by configuration the event caused by an alarm si¬ gnal can be made to cause one or more picture captures from one or more video sources v. Under the control of the microproces¬ sor the video source selection switch (7) places the required video signal onto signal line (8) allowing sync separator (9) to provide synchronising pulses to pixel clock (10) and raster address counters (11). The binary address count provided by these counters changes every four pixels thus providing a count at one quarter of the fast scan rate. In addition the video signal (8) is also fed to video peak detectors (12). Under the control of the active area signal (13) the peak detectors pick out the blackest and whitest parts of the picture but only for those parts of the picture that are to be digitised. The vol¬ tage output (14) from the peak white detector is then used to define the upper limit of digitisation level (corresponding to maximum digital code). Similarly the voltage output from the peak black detector is used to define the lower limit of digi¬ tisation level (corresponding to minimum digital code). The A/D convertor (16) uses the voltages from the peak detectors and provides a 6 bit output for each pixel. In order to inter¬ face with the video memory array at a slow enough cycle rate the digitised pixels are fed through the video shift register (17) so that the video memory storage rate is one quarter of the pixel sampling rate. Pixels are written into the video me- ory (18) under the control of the capture request logic (19). Once triggered by the microprocessor (1) the capture logic waits for the start of the next video field and then begins to issue write pulses to the memory (18) until the field is com¬ plete. Since the video memory can hold up to four pictures the identification of the store to be written is provided by the write store select signal (20). So that it is possible to determine exactly what area of the picture is being digitised the active area signal (13) is fed to the active area insertion circuit (21). This causes the digitised area to be shown on a monitor (M) in circuit (21). This causes the digitised area to be shown on the monitor in higher intensity and higher contrast than its surroundings. If an alarm or other event is deemed to be significant (as defined by user configuration) the microprocessor will begin an auto calling sequence to a predefined telephone number via the telephone line interface (22). Once the connection has been established with the receiver unit data is transferred via the F.S.K. generator (23) and F.S.K. demodulator (24). Dial tone detector (25) and Carrier detector (26) provide normal tele¬ phone line and modem supervision. Data is transmitted at all times except when a slow scan picture is requested by the re- ceiver.

Additional telephone line supervision is provided by the detection of exchange battery voltage. This voltage must be present at all times for a telephone connection to be estab- lished and maintained. In order to detect this the following scheme is adopted.

With the telephone line in an offline condition a low amplitude signal is sent from the F.S.K. generator (23) to the telephone line interface (22). The telephone line interface (22) is so ar¬ ranged that it's impedance partially matches that of the F.S.K. modulator when exchange battery is present and completely mis¬ matches it when exchange battery is absent. This leads to a change in the amplitude of the reflected signal such that a low amplitude reflection occurs when partially matched and a high amplitude when not matched. This signal is in turn either detec¬ ted or not by the carrier detector (26). The signal from the carrier detector then gives a direct indication of the presence or absence of exchange battery voltage.

When slow scan mode is entered the microprocessor begins to read pixel data from the video memory array (18). This is achieved by the processor providing the address of the required pixel to the address selection multiplex (27). This address contains the store select identity in addition to the pixel address within the store. Once the address is set up the processor activates the pixel request logic (28) which waits for the next read access period and produces the required memory access signals to read the pixel and clock it into the pixel output latch (29). Pixels read in this way are passed through a buffer in the microprocessor to equalise timing and thence to the F.M. modulator (23). All timing and synchronisa¬ tion signals are provided by the processor. To improve the ability of the receiver unit to accurately derive the slow scan timing signals from the demodulated F.M. waveform the phase of the transmitted F.M. carrier is synchronised to the leading edge of each slow scan line sync pulse. Since every line sync pulse has the same duration the phase of the F.M. carrier in relation to the trailing edge of the sync pulse will be the same irrespective of the data content of the previous line. Variation in timing for each line of slow scan caused by the high modulation index used is thus virtually eliminated. In order to increase the effective speed of slow scan transmission an interlaced scheme is adopted. On the first slow scan field only the even memory rows are accessed. At the end of this field a second scan is started but this time the odd rows are accessed. To stop the picture at the receiver being interlaced with a previous picture the receiver writes both the odd and even rows on the first interlaced field.

Configuration information is maintained at the transmitter unit in an electrically eraseable PROM memory (1). Data is thus non volatile but easily modified by suitable commands to the opera- ting software. These commands are generated by a special pro¬ gramming software running on a standard P.C. The P.C. can be connected directly to the transmitter unit or remotely via the data channel set up with a receiver unit. Remote configuration provides all the facilities of local configuration.

In the receiver a microprocessor control and coordination sub¬ system (30) handles all the display, Man Machine Interface and communication aspects of the unit. The telephone line interface (31) responds to an incoming call by passing the ringing vol- tage cadence to the microprocessor for assimilation. If all conditions are right then the microprocessor waits for a gap in the ring cadence and then answers the call by activating the line holding loop in the telephone line interface (31). After going on line the receiver attempts to establish data communi- cation with the calling transmitter. Serial data sent from the microprocessor is modulated for transmission by the F.S.K. mo¬ dulator (32). The signals thus generated are low pass filtered by filter (33) and passed to the telephone line interface (31) and thence to line. F.S.K. signals received from the remote transmitter are passed via band pass filter (34) to remove un¬ wanted out of band noise and then to the F.S.K. demodulator (35). The demodulated serial data is then passed to the micro¬ processor for error checking. The carrier detect circuit (36) provides for the determination of the presence of both data and slow scan carrier tones. A similar scheme is adopted for the detection of exchange battery voltage as used in the transmit¬ ter unit except that the dial tone detector is employed. The dial tone detector (37) is used to confirm the presence of telephone dial tone before routing digits are sent to line when a call is initiated from the receiver. Outgoing calls are made when it is required to check a transmitter unit's operation in the absence of an alarm situation. When slow scan pictures are transferred from the transmitter unit the F.M. signals pass through the bandpass filter (34) and are demodulated by the F.M. demodulator (50). The analogue slow scan signal is then passed to the analogue to digital converter (51) which produces a 7 bit output. Even though the transmitter unit only provides a 6 bit signal (equivalent to 64 gray shades) the extra gray scale resolution provided by the receiver's 7 bits (equivalent to 128 gray shades) provides for improved picture quality due to the analogue nature of the transmission scheme adopted. The analogue slow scan signal is also fed to the sync separation circuit (52) where an accurate timing reference is obtained.

The Man Machine Interface on the receiver unit is provided via a dedicated keypad with integral indicators (38) for user prompting and command entry. In addition the monitor (39) pro¬ vides for both a textual display (for information such as chro- nological event lists) and a picture display with associated textual identification at top and bottom. The keypad and asso¬ ciated indicators (38) are driven directly from the micropro¬ cessor (30). The monitor display (39) is handled as follows: Under the control of the microprocessor (30) the display con- troller (40) provides the required signals to access the pic¬ ture and text memory (41). This memory is made up of standard video DRAM (VRAM) and is thus, by nature, dual ported. The memory is arranged so that each screen pixel has one byte (i.e. 8 bits) associated with it. Seven of the serial outputs (bits) of the memory are passed to the digital to analogue con¬ verter (42) to provide 128 gray shades when a picture is dis¬ played. The other one serial output(bit) bypasses the conver¬ ter and both this and the converted signal are fed to the pic- ture or text selection switch (43). This switch is operated at suitable moments in the raster display by the display control¬ ler (40) which is in turn overseen by the microprocessor to provide full text or mixed text and picture displays. The basic timing reference for the display is provided by the pixel clock (44). This reference is fed to the display controller (40) and T.V. sync generator (45). The sync generator provides the sepa¬ rate line and field synchronisation signals for use by the dis¬ play controller (40) in formatting the screen. A mixed sync signal is also produced by the T.V. sync generator (45) which is fed to the sync insertion circuit (46). The syncs are added to the video signal fed from the picture or text switch (43) thus providing a standard composite output signal.

Two serial channels are provided for connecting external data equipment. One channel, the printer interface (47), provides for the connection of a standard serial printer thus allowing the hard copy logging of all event communication with the transmit¬ ter unit. The second channel, the computer interface (48), pro¬ vides for the connection of a configuration computer that can be used to read or write the receiver configuration memory (49) or remotely read or write the connected transmitter unit's configu¬ ration memory.

Once data communication has been established between the recei- ver and transmitter units the receiver prompts the operator by an audible buzzer, a flashing indicator on the front panel (38) and the display of an identification message on the monitor (39). Once acknowledged by the operator the buzzer and flashing indicator are cancelled and the display changed to show a chronicological list of transmitter unit events. Each event has displayed with it an absolute time of occurance. The time shown for each event is not provided directly by the transmitter unit but is calculated by the receiver from a relative time sent by the transmitter unit along with each event. The time reference for the events in any one communication call is the first sig¬ nificant event of the call (i.e. the event that initiated the call). All subsequent events are timed in relation to this first event. When communication is established between the transmitter and receiver units the receiver must determine the absolute time that relates to the time of the first or reference event. This is achieved by having the transmitter unit send its current relative time reference as soon as communication is achieved. By substracting this relative time from its current absolute time (by means of a watch T e.g. provided in the Receiver Unit) the receiver determines the absolute time for the reference event. All subsequent absolute event times are the obtained by simply adding the relative time sent with the event to the absolute reference event time.

If pictures are available at the transmitter unit this is signalled to the operator by flashing transmit indicators on the key pad (38). Pictures are always stored in high definition at the transmitter unit but the operator is provided with three possible transmission options. A full screen low definition picture can be transmitted in 8 seconds. A full screen high definition picture can be transmitted in 32 seconds. If three or four pictures have been stored at the transmitter unit then a quad picture of 3 or 4 low definition pictures can be transmit- ted in 32 seconds. Once transmitted the operator has the option to re-transmit the same picture in the same or different format. The same format may be chosen if telephone line noise has cor¬ rupted some important detail of the picture. An alternative format may be chosen if, for instance, a picture was originally transmitted in low definition and it is thought that more picture detail would be useful.

In addition to the event related picture capture and transmis¬ sion the receiver also provides for continuous monitoring from any one or all four transmitter video sources. By pressing the relevant slow scan key the receiver instructs the associated transmitter unit to first capture and then send pictures in any one of the three formats. Re-transmission is again provided as described for event related pictures.

The receiver unit also provides remote control and tellback of the relays at the associated transmitter. The fault log main¬ tained by the transmitter unit can be read on request as an aid to system fault location.

In mobile applications (fig. 3) the transmitter (fig. 1, 53 fig. 3) and/or receiver units (fig. 2, 54 fig. 3) are used in conjunction with a non-wired low bandwidth connection such as Cellnet (Cellular Network) or radio telephone 56. Depending on application, the dialled digits from either transmitter 53 or receiver 54 can be inhibited allowing a direct or presetected communication path to be used. Radio transceivers 55 for wireless communication can be integrated into associated transmitter 53 or receiver 54 if required.

These applications would involar transmitting "slow scan" pictures via a Radio/Cellular telephone 56 to a base station 55 eg. "Scene of Crime/Accident etc" pictures from a police car transmitted to the police station. Other possible mobile application include servicing, on-site fault diagnosis etc.

For hand held total mobility it is also possible to integrate video camera V, slow scan transmitter unit 53 and mobile phone 56 into a small battery powered unit 57 on the transmitter side, or to integrate base station phone 55, slow scan receiver unit 54 and monitor T.V. into a small unit 58 on the receiver side of the system.

Claims

1. Integral Slow Scan and alarm System comprising

- Means (1) to receive event data from external alarm devices (2,3,5) and picture data from one or more video sources (7) of premises to be surveyed

- means (1,18) to store event data, picture data, along with an associated time reference

- means (1,23,24) to transmit said stored data once an alarm event has been encountered via a preselectable low band width channel to a preselectable receiving unit

- means (39) associated to said receiving unit to display said transmitted data.

2. Integral slow scan and alarm system according to claim 1 comprising means (7) for video input switching allowing the selection of one of said video sources.

3. Integral slow scan and alarm system according to any of claims 1 or 2 comprising queuing means (18,1,40,30,41) to store said event data and said picture date in chronological order.

4. Integral slow scan and alarm system according to claim 3 comprising timing means (30,1) designed such that the relative time after events stored by the queueing means stored alongside the associated event.

5. integral slow scan and alarm system according to any of claims 1 to 4 comprising one or more event and slow scan storage and transmission units dedicated to the functions of event and slow scan storage and transmission and one or more event and slow scan reception and display units dedicated to the function of event and slow reception and display.

6. Integral slow scan and alarm system according to claim 5 wherein said storage and transmission unit comprises

- a microprocessor controlling -means (1) for co-ordinating all unit activities and handling event data and slow scan trans- mission

- a memory (18) for storage of digital video information and capable of being read by said microprocessor controlling means

- an alarm input means (4) for interfacing external alarm detection devices to the microprocessor controlling means

- an alarm display (D) means for indicating of the state of the external alarm detection devices

- a data modulation and de-modulation means (23,24) for commu¬ nication of status and control information via a low band width channel (22) and

- a slow scan modulation means (23) for transmission of slow scan picture information.

7. Integral slow scan and alarm system according to any of claims 1 to 5 wherein said event and slow scan reception and display unit comprises:

- a microprocessor controlling means (30) for co-ordinating all unit activities and handling event data and slow scan reception - a memory (41) for storage of digital video information and capable of being written by the microprocessor controlling means

- a data modulation and de-modulation means (34,35) for communication of status and control information and a low band width channel

- a slow scan de-modulation means (50) for reception of slow scan picture information and

- an interface means (38,47,48) for providing an output of said event data to external equipment.

8. Integral slow scan and alarm system according to any of claims 1 to 7 comprising

- means (1,23) to accurately derive the slow scan timing signals from a de-modulated F.M. waveform by synchronizing the phase of a transmitted F.M. carrier to the leading edge of each slow scan line synchronous pulse.

9. Integral slow scan and alarm system according to any of claims 1 to 8 comprising - means (1,18) to provide a first slow scan field by access of a first set of memory rows such as odd rows

- means (1,18) to provide a second slow scan field by access of a second set, different from the first set of memory rows such as even rows and - means to write both sets of rows on the first or the second field.

10. Integral slow scan and alarm system according to any of claims 1 to 9 wherein the picture data storage means (18) are designed to always store the picture data in high definition and the system comprising means to display the picture data at different stages of definition and to transmit the picture data at different speeds according to the stages of definition.

11. Integral slow scan and alarm system according to any of claims 1 to 10 comprising means (22,26,37) to supervise the low bandwidth channel such as telelphone line by detection of exchange battery voltage.

12. Integral slow scan and alarm system according to any of claims 1 to 11 comprising means (1) to establish a definable sequence of pictures for each alarm, depending on nature of alarm and the configuration of the system.

13. Integral slow scan and alarm system according to any of claims 1 to 12 comprising means (1,12,51) including video peak detectors (12) to define the upper and lower level of digisation over a predifined area and/or means (51) to convert received picture data into higher resolution data to achieve maximum picture quality.

14. Integral slow scan and alarm system according to any of claims 1 to 13 comprising means (36,37) to determine the presence of both data and slow scan carrier tones and/or to check a transmitter unit's opera¬ tion in the absence of an alarm situation.

15. Integral slow scan and alarm sytem according to any of claims 1 to 14 wherein a single low bandwidth channel such as a telephone line is used for both control data and slow scan picture information transmission.

16. Integral slow scan and alarm system according to any of claims 1 to 15 wherein the system is designed for mobile applications where either the transmitter means (fig. 1, 53) and/or the receiver means (fig. 2, 54) are associated to means (55) for providing a wireless communication.

17. Integral slow scan and alarm system according to claim 16 wherein said means (55) are integrated with said transmitter and/or receiver means (53, 54).

18. Integral slow scan and alarm system according to any of claims 16 or 17 wherein a small internally powered unit (57, 58) is provided comprising said transmitter means (53, V) or said receiver means (54, T.V.) and respective means (55) for wireless communication.

19. Apparatus to provide absolute time of occurance to an event in an alarm system having transmitter units (fig. 1) and receiver units (fig. 2) comprising

- means (1) associated to the transmitter to determine a current relative time between a significant reference event initiating a communication call to the receiver and subsequent events

- means (30) associated to the receiver to determine the abso¬ lute time that relates to the time of the reference event by having the transmitter unit send its current relative time and substracting this relative time from a current absolute time present at the receiver

- means (30) associated to the receiver to determine the abso¬ lute event time of a subsequent event by adding the current relative time send with the subsequent event to the absolute time of the reference event.

20. Apparatus according to claim 19 wherein said apparatus is arranged within a slow scan alarm system comprising means (39) to display each event with the absolute time of occurance.