Digital output unit

Details Digital output unit Digital output unit

2000-05-31

2002-05-21

Pham, Chi (Department: 2731)

Pulse or digital communications

Testing

Reexamination Certificate

active

06393053

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a digital input unit with means for detecting wire breakage and with at least one input channel to which an input signal can be supplied over a line; this input signal is transmitted by electrical isolating means of an evaluation unit that assigns the level states of the input signal above a first threshold to a logical “1” and the level states between a voltage greater than 0 V, but below a second threshold that is smaller than the first threshold, to a logical “0”.
BACKGROUND INFORMATION
A digital input unit of this type is described in Siemens catalog ST 70, 1997 edition, pages 4/16 and 4/17. To enable electrical isolation, it is customary to provide each input channel with a first and a second optocoupler, one of which is provided to transmit the input signal, i.e., to transmit status information logical “0” and logical “1”, while the other is provided to transmit wire breakage information to a wire breakage monitoring unit that monitors the lines connected to the input circuit.
SUMMARY
An object of the present invention is to simplify the transmission of status and wire breakage information in a digital input unit.
The digital input unit according to the present invention has the advantage that it requires only one optocoupler for transmitting the status and wire breakage information. This significantly improves EMC performance, particularly in digital input units with multiple input channels.


REFERENCES:
patent: 3803355 (1974-04-01), Fiedler et al.
patent: 3942098 (1976-03-01), Haass
patent: 5119096 (1992-06-01), Marschall
patent: 5554947 (1996-09-01), Saitou et al.
patent: 5623190 (1997-04-01), Tajima et al.
patent: 676 393 (1991-01-01), None
patent: 0 735 375 (1996-10-01), None
K. Kirk, “Remote Logic Drive”, New Electronics, vol. 9, No. 22, Nov. 16, 1976, p. 19, XP002032864, Described in the specification.
Siemens Catalog ST 70, 1997 Edition, pp. 4/16-4/17, Described in the specification.

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