Telephonic communications – Emergency or alarm communications
Reexamination Certificate
1997-07-22
2001-05-01
Kuntz, Curtis (Department: 2643)
Telephonic communications
Emergency or alarm communications
C379S026020, C379S047000
Reexamination Certificate
active
06226357
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to alarm panels for security systems and in particular, relates to alarm panels having a microprocessor and associated communication arrangement for contacting a monitoring station using the telephone system.
BACKGROUND OF THE INVENTION
An alarm panel receives signals from a host of sensors and processes these signals to determine whether an alarm condition or other reportable event has occurred. The alarm panel is typically connected to a telephone line and uses this telephone line to report the alarm condition or a reportable event to a control station. The telephone line is normally shared by the alarm panel with other downstream telephone devices but the alarm panel has priority and the ability to interrupt communications of downstream devices.
Public telephone systems vary and different regulatory bodies have developed their own specifications that alarm panels and other devices must meet to be approved.
These different specifications are not easily met with a single cost effective circuit and different circuits have been developed to meet different regulatory specifications. Separate designs for each different market increases manufacturing costs and limits manufacturing flexibility. In France, for example, regulations require that the current draw of the device is limited to between 25 and 60 mA. This is in contrast to the U.S. and Canadian requirements which do not require the circuit to be currentlimited.
As will be more fully explained, an alarm panel switches between active and a passive state. In the active state, the alarm panel is using the telephone line to communicate with a remote computer to communicate, for example, with the owner at a remote location. In the passive state, the alarm panel monitors the telephone line for a ring signal and may also conduct tests to determine line integrity.
Control panels have previously used four or five optocouplers to electrically isolate the microprocessor of the alarm panel from the telephone line. It is also known to use only two optocopulers to isolate the alarm panel microprocessor from the telephone line; however, this 2 optocoupler design has serious compromises in the operating characteristics thereof.
SUMMARY OF THE INVENTION
An alarm panel of a security system, according to the present invention, comprises a microprocessor for processing signals from security sensors and appropriately, communicating with a remote computer from time to time, using a telephone line connection. A receive optocoupler and a transmit optocoupler form part of a communication circuit connecting the microprocessor to the telephone line connection which circuit is powered by the telephone line. The receive and transmit optocouplers electrically isolate the microprocessor from the communication circuit which is directly connected to the telephone line. The communication circuit includes two subcircuits connected to the telephone line connection. These subcircuits are an AC ring signal detection subcircuit and an active communication subcircuit, each of which share the receive optocoupler.
The active communication subcircuit operates in a quiescent state or an active state. In the quiescent state the telephone line is separated from the communication subcircuit by a large resistance and there is very little current draw. In the active state the line is seized and the off-hook signals have been generated by the alarm panel. The large resistance is bypassed and full two-way communication is possible over the telephone line. There is a much higher current draw in this state.
The AC ring signal detection subcircuit monitors the telephone line connection to detect a ring signal and the signal is passed to the microprocessor. The DC communication subcircuit cooperates with the microprocessor to produce an off hook condition allowing the microprocessor to form a two-way communication through the optocouplers and the telephone line connection when the microprocessor provides an off-the-hook signal to the DC communication subcircuit through the transmit optocoupler. The AC ring detection subcircuit is designed to be DC voltage independent, have low power consumption and is designed to pass the AC component of a telephone ring signal to the receive optocoupler. The communication subcircuit is designed to determine the DC current characteristics of the communication circuit when the circuit has seized the line and the line has gone “off-hook”. The ring detection characteristic can be modified by varying the AC ring detection subcircuit without any appreciable effect on the communication subcircuit. Power consumption and DC voltage characteristics of the communication circuit can be modified by changing components without any appreciable effect on the ring detection characteristics of the AC ring detection subcircuit.
The alarm panel, as defined above, is easily customized by modifying the communication subcircuit without altering the ring detection subcircuit, while still allowing the subcircuits to share the receive optocoupler. In this way, modifications can be made to either of the subcircuits to meet any particular standard and these modifications do not change the characteristics of the other subcircuit. This provides a great deal of flexibility allowing individual components of the subcircuits to be changed to meet specific requirements.
According to a preferred aspect of the invention, the communication subcircuit include a telephone line monitoring for determining if the telephone line is operable. For example, the telephone line could be cut and if this is the case, the alarm panel would like to have knowledge of this interruption of service. The telephone line monitoring arrangement includes a charge device in the communication subcircuit which is charged by a low current in the subcircuit in the quiescent state. The charge device is selectively discharged by the microprocessor producing and transmitting a signal or series of signals through the transmit optocoupler. When the microprocessor does transmit a signal, it results in a discharge of the charged device which produces a discharge signal provided to the microprocessor through the receive optocoupler. If the telephone line is not operative, the charge device is not being charged and does not produce a discharge signal. The failure to detect such a discharge signal indicates to the microprocessor that the telephone line is not available.
Accordingly to a further aspect of the invention, the subcircuits are joined at the telephone line connector and at a common section which includes the receive optocoupler.
According to yet a further aspect of the invention, the communication subcircuit includes a power dissipation arrangement which, in the event of a transient high voltage condition, dissipates the power and limits the current in the subcircuit to a design maximum, prior to reaching the maximum design transient voltage.
REFERENCES:
patent: 3982242 (1976-09-01), Sheffield
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patent: 4097690 (1978-06-01), Kuntz
patent: 4262283 (1981-04-01), Chamberlain
patent: 5457730 (1995-10-01), Rounds
patent: 5517547 (1996-05-01), Ladha etal.
patent: 5799062 (1998-08-01), Lazzara et al.
patent: 4106023 (1992-08-01), None
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patent: 2298760 (1996-09-01), None
Patent Abstracts of Japan, vol. 015, No. 127 (P-1185) Mar. 27, 1991 & JP 03 012797A (Yoshinori Kojima Jan. 21, 1991.
Digital Security Controls Ltd.
Kuntz Curtis
Ramakrishnaiah Melur
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