Communications: electrical – Condition responsive indicating system – With particular coupling link
Patent
1987-12-04
1989-04-25
Crosland, Donnie L.
Communications: electrical
Condition responsive indicating system
With particular coupling link
340505, 34030915, 34082507, G08B 100, H04Q 130
Patent
active
048251968
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a signal transmission circuit of a fire/security protection system, and more particularly, it relates to a signal transmission circuit of a fire/security protection system which transmits a signal from a signal processing portion provided in a control panel or terminal device of the fire/security protection system and which, even when trouble occurs in said control panel and the like, still allows other slave units and the like in normal condition to transmit the signal to the signal line without being occupied by the control panel or slave unit in trouble.
BACKGROUND TECHNOLOGY
Control panels and terminal devices (e.g. slave units, fire sensors, fire detectors, intrusion detectors, fire protection means, smoke venting means, fire extinguishing means) of fire/security protection systems such as fire alarm systems and security systems are equipped with transmission circuits, and it is necessary to check if the transmission circuits have properly transmitted their predetermined signals.
The following method is considered to be suitable for this check. The signal which should be transmitted from the transmission circuit is stored in the memory circuit, and the signal which has been transmitted from said transmission circuit is received by the receiving circuit. This received signal is compared with the signal stored in the memory circuit, and if they match, it means that the transmission circuit has properly transmitted the signal.
Nevertheless, if a trouble occurs in the receiving circuit, it is not possible to detect the signal transmitted from the transmission circuit, and descrimination means such as a CPU judges that no signal has yet been transmitted from the transmission circuit. Therefore, even after the parallel-serial converter has completely sent the signal to be transmitted off to the transmission circuit, the CPU still keeps the transmission circuit in a state ready for signal transmission, and consequently the signal line remains occupied by the terminal device. Therefore, there is such a problem that the control panel or other slave units can not transmit signals to the signal line.
DISCLOSURE OF THE INVENTION
The present invention is made in view of the above circumstances and with the objective of offering a signal transmission circuit which transmits a signal from a signal processing portion provided in a control panel or terminal device of a fire/security protection system and which, even if trouble occurs in the control panel or a terminal device such as a slave unit, still allows the control panel or any other slave unit in normal condition to transmit the signal to the signal line without being occupied by the control panel or slave unit in trouble.
The present invention has been made to achieve said object. Namely, according to the present invention, a signal transmission circuit is provided with a control panel or a terminal device of a fire/security protection system so as to transmit the signal from said control panel or terminal device to a signal line, said signal transmission circuit comprising a signal transmitting means set to any enable state when transmitting a signal under the control of said signal processing portion, a signal detecting means to detect the signal transmitted from said signal transmitting means to the signal line, a timer means which is set when the signal is transmitted and is reset by the detection output from said signal detecting means, and signal transmission control means to turn off said signal transmitting means when the time count output of said timer means is present during a predetermined time interval.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing an embodiment according to the present invention;
FIG. 2 is a circuit diagram showing the transmission circuit and receiving circuit shown in FIG. 1 more concretely; and
FIG. 3 is a flowchart showing the operation of the above embodiment.
BEST MODE FOR EMBODYING THE INVENTION
FIG. 1 is a block diagram showing the present
REFERENCES:
patent: 4550311 (1985-10-01), Galloway et al.
Crosland Donnie L.
Nohmi Bosai Kogyo Kabushiki Kaisha
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