A remote alarm circuit provides visible and audible signals to indicate that there is little unused space left on magnetic and optical tracks on disks used to record voice signals in a group of three multichannel voice recorders. In the particular application for which the remote alarm circuit was built, the voice recorders are required to operate without interruption, but the technicians responsible for the continuous operation of the voice recorders perform most of their duties on a different floor of the building in which the voice recorders are located. The remote alarm circuit gives sufficient advance warning to enable the technicians to go to the voice recorders and change recording disks in time to ensure continuity of recording.
The circuit (see figure) includes a sensor in each voice recorder that closes a switch when the unused space on the recording disk falls below a preset minimum. A sensor switch closure indicates a fault condition in which an audible alarm activates together with a light emitting diode (LED) for the corresponding fault. Three current steering diodes make the voltage across, and current through, the audible alarm independent from the number of simultaneous faults. This keeps the alarm tone consistent despite the number of alarms.
For verifying the alarm panel, normally-open push-button switches are wired in parallel with the remote sensor switches. This arrangement decouples the test circuitry from the alarm circuitry, which (1) allows each alarm to be tested without the presence of a fault condition on a voice recorder, and (2) prevents any failure in the test circuitry itself from disabling an alarm indication when an actual fault condition is present on a voice recorder. Pressing a push-to-test button causes the audible alarm to signal and the corresponding voice recorder LED to light. A green LED is used as a pilot light.
This work was done by Harold Minuskin of NASA’s Jet Propulsion Laboratory and by John Pastor of XteQ, Inc. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Electronics/Computers category. NPO-40150
This Brief includes a Technical Support Package (TSP).
Circuit Indicates That Voice-Recording Disks Are Nearly Full
(reference NPO-40150) is currently available for download from the TSP library.
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Overview
The document is a Technical Support Package from NASA’s Jet Propulsion Laboratory (JPL) concerning a circuit designed to indicate when voice-recording disks are nearly full. It is identified as NPO-40150 and is part of NASA Tech Briefs, which aim to share aerospace-related developments with wider technological, scientific, or commercial applications.
The document outlines the technical specifications and operational details of the circuit. It includes information about the components involved, such as recorders and test alarms, and describes the power supply system. The power LED, which indicates the operational status of the device, is connected after the fuse to ensure it extinguishes in the event of a power failure, providing a clear visual cue for users.
The design specifications are detailed, including the mounting requirements for terminal blocks, which utilize flat-head screws to ensure a flush finish with the panel. The document specifies the dimensions and characteristics of various components, such as the test alarm switches and the LED indicators, emphasizing the importance of precise engineering in the device's functionality.
Additionally, the document serves as a resource for further assistance, directing readers to the NASA Scientific and Technical Information (STI) Program Office for additional information on research and technology in this area. It provides contact details for the STI Help Desk, including a telephone number, fax number, and email address, facilitating access to further resources and support.
The document also includes a disclaimer stating that the United States Government and its representatives do not assume liability for the use of the information contained within, nor do they guarantee that such use will be free from privately owned rights. This notice underscores the importance of understanding the legal implications of utilizing the technology described.
Overall, the Technical Support Package encapsulates critical information about a specific technological advancement in voice recording systems, highlighting NASA's commitment to sharing knowledge and fostering innovation in aerospace technology. It serves as a valuable reference for engineers, researchers, and industry professionals interested in the applications of this technology.
