EP0265935B1 - Infrared transmitter for coded messages using a fixed code and a great number of combination facilities - Google Patents

Description

The invention relates to a code message infrared transmitter with a fixed code and a large number of possible combinations.

Code message transmitters are used, for example, for the remote control of security systems, particularly in the automotive industry. These transmitters are generally encoded by interrupting certain power supply lines. This mechanical and thus visible coding can easily be read optically and the number of possible combinations is also limited.

The present invention has the purpose of eliminating these disadvantages of the known transmitters.

A device is known (FR-A-2573881) which overcomes these disadvantages by providing a programmable electrical memory, a clock which addresses the content of the memory, a pulse generator, the input of which is supplied with the content of the memory Amplifier, which is connected to the output of the pulse generator and which drives an emitting diode, and has a blocking device which controls the clock generator and blocks the transmitter after sending a message.

This known device offers a large number of possible combinations, but has the disadvantage that the blocking device is triggered by opening the switch which causes the code message to be sent. This makes it necessary to keep the switch pressed until the end of each program. An accidental opening of the switch also leads to the sudden termination of the transmission process.

Therefore, the object of the invention is to improve the blocking device of a code message infrared transmitter so that the blocking device is independent of a switching operation and only effective at the end of each transmission process.

This object is achieved in that the blocking device has a gate, the input of which is connected to an RC time constant element, which is loaded by a sequence of bits of the high-level state "1" sent at the end of each message so that the gate is binary Value changes.

• Abbildung 1 ein Blockschaltbild eines Senders gemäß der Erfindung darstellt und
• Abbildung 2 ein Schaltbild des Senders gemäß Abbildung 1 für ein Ausführungsbeispiel darstellt.

The invention will be elucidated by the following description, in which reference is made to the accompanying drawing, in which:

• Figure 1 shows a block diagram of a transmitter according to the invention and
• Figure 2 shows a circuit diagram of the transmitter according to Figure 1 for an embodiment.

The device contains a memory 1 in a programmable series version, the reading function of which is controlled by the pulses emitted by a reading pulse generator 2, oscillator or clock generator. The content of the memory 1 is fed to a pulse generator 3. The generator 3 feeds an amplifier 4 which feeds an emitting diode 5. The content of the memory 1 is also fed to a device for blocking at the end of the message 6, which monitors the encoder 2.

bewirkt. Das System kann, je nach Art des verwendeten Speichers, erst nach Unterbrechung der Einspeisung oder nach Entladung der Kapazität C wieder senden.8 memory bits are used to define a sent byte. The byte sent contains a synchronization bit and data bits 0 or 1. In order to block the system at the end of the transmission, all bits of the last sent byte (which comprises 8 bits) are set to 1, which means that the capacity C (Figure 2) of the blocking device is sufficiently charged 6 allows the voltage at the input of the connection point IC to tilt and block the oscillator $\frac{\text{1}}{\text{2nd}}$

causes. Depending on the type of memory used, the system can only transmit again after the supply has been interrupted or after the capacity C has been discharged.

Claims (1)

1. An infrared transmitter for coded messages, using a fixed code and a large number of possible combinations, comprising a programmable, electrical serial memory (1), a clock signal generator (2) which addresses the content of the memory (1), an impulse generator (3) to the input of which the content of the memory (1) is supplied, an amplifier (4) which is connected to the output of the impulse generator (3) and which operates an emitting diode (5), and a blocking device (6) which controls the clock signal generator (2) and blocks the transmitter after a message has been sent, characterized in that the blocking device comprises a gate (IC1) the input of which is connected to an RC-time constant element which is charged by a sequence of bits having the high level state "1", transmitted at the end of every message, in such a way that the gate (IC1) changes its binary state.

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