Abstract: In a preferred data capture system, a RF data terminal is capable of use alone or with any of a series of scanner modules incorporating diverse scanner technologies such as CCD bar code scanning, area image data reading, cyclically swept laser beam bar code scanning, and RF identification label scanning. In each case, a frontal operating panel of the RF terminal--scanner system is held facing the user during scanning, whether the system is held with the right or left hand. Scanner data is supplied to the-RF unit by mating connectors or the like. From the RF unit, the scanner data may be transmitted on-line to a host computer or other receiving station. The family of scanner modules may provide respective laser scanners with respective different wavelengths of illumination so that an optimum module may be selected for reading respective bar codes of differing color characteristics. The family is readily upgraded to incorporate new light sources of greater efficiency and/or more advantageous spectrum.

Abstract: In large multi-tiered hierarchical alarm systems for high capacity telecommunications transmission systems, it is important to notify the maintenance craft of only the highest alarm, and to notify only when the alarm has been validated by persisting for a sufficiently long time. Advantageously, this is accomplished by timing alarms and freezing the timing when a higher level alarm is detected. If the higher level alarm is no longer present, timing on the lower level frozen alarm signal continues until there is a timeout. A timed out alarm is reported to the maintenance craft.

Abstract: A method and apparatus for detecting the presence of a particular constituent in a sampled atmosphere. The sampled atmosphere is drawn along two substantially identical flow paths, each path containing a detector. The flow of the particular constituent is delayed along one path only but not the other path to separate, in time, the signals from the two detectors. Means are provided for obtaining a resultant difference signal and for utilizing the difference signal to provide a positive identification of the presence of the particular constituent in the sampled atmosphere.

Abstract: A method and apparatus for detecting the presence of a particular constituent in a sampled atmosphere. The sample is drawn through two substantially identical flow paths, each path containing a detector. The conditions prevailing in one of the flow paths is such as to convert the particular constituent into matter which will not produce a response in the associated detector. When the particular constituent is vapor originating from an explosive the conversion can be by heating the flow path to a temperature at which the vapor breaks down into components which do not produce a response in the associated detector. In the absence of the particular constituent in the sampled atmosphere the signals from the two detectors are substantially equal but the presence of the particular constituent results in a difference in signals from the two detectors.

Abstract: Baseline drift and noise can produce difficulties in registering signals quantitatively without recourse to frequent rezeroing of the registering instrument. The invention provides a circuit in which the registering instrument only functions when a required signal is to be noted, the instrument at all other times being at a zero reading. The characteristics of a signal to be registered will be known. The circuit includes a differentiator which notes the rate of change of incoming signals and operates a switching device upon detecting a required rate of change to enable the signal to pass to the registering instrument. At all other times the registering instrument is isolated by the switching device.