Browse Prior Art Database

Fault-Tolerant, Single-Line, Frequency-Dependent Safety Control

IP.com Disclosure Number: IPCOM000115275D
Original Publication Date: 1995-Apr-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Pole II, EJ: AUTHOR

Abstract

Disclosed is the use of a single control line providing a signal used to control a device under conditions in which an unsafe condition could be expected if the safety control does not function properly. A meaning is attached to the frequency of the signal, with a control output being sent over the line to detection circuitry, the output of which is activated when the correct frequency is received. This detection circuitry may consist of a narrow band-pass filter set at the control frequency. With this method, the possibility of providing a false indication of the signal, even with the occurrence of a number of simultaneous faults, diminishes to a vanishing level. Therefore, this method may be used, for example, to control a laser-driven holographic bar code scanner from a remote point.

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Fault-Tolerant, Single-Line, Frequency-Dependent Safety Control

      Disclosed is the use of a single control line providing a
signal used to control a device under conditions in which an unsafe
condition could be expected if the safety control does not function
properly.  A meaning is attached to the frequency of the signal, with
a control output being sent over the line to detection circuitry, the
output of which is activated when the correct frequency is received.
This detection circuitry may consist of a narrow band-pass filter set
at the control frequency.  With this method, the possibility of
providing a false indication of the signal, even with the occurrence
of a number of simultaneous faults, diminishes to a vanishing level.
Therefore, this method may be used, for example, to control a
laser-driven holographic bar code scanner from a remote point.

      Alternately, several control signals, each at a different
frequency, can be transmitted to a unit through a mixer and a cable.
In this case, the unit has a set of detection circuits, each of which
is set at a frequency used for one of the control signals.  Each of
the detection circuits actuates a function based on the presence of a
particular signal frequency on the control line, allowing a single
line to communicate a number of states simultaneously.