Abstract: An audience response system is provided. In various implementations, the response system includes a base station, handheld units, and a wireless network. The response system may have a prompted mode and an unprompted mode of operation. In the prompted mode of operation, the base station transmits questions to the handheld units over the wireless network. The questions are displayed to users on their handheld units. The users respond to the question, and their responses are transmitted to the base station via the wireless network. In the unprompted mode, answer templates are transmitted and displayed to the users, with the actual questions being conveyed in some other manner, such as verbally or by written handout.

Abstract: A wireless classroom response system includes multiple wireless networks, each serving a different classroom. Each network has a computer located proximate to the classroom that the wireless network serves. The computer executes a communications server and an application program, wherein the application program facilitates classroom activities. The system also includes a wireless access point located proximate to the classroom. The wireless access point is communicatively linked to the computer. The system also has a plurality of handheld units. Each handheld unit displays, to a user, a list of the networks, and receives a user input indicating which one of the wireless networks the handheld unit should connect. The handheld unit connects to the chosen wireless network, thereby becoming a node in the wireless network. It also transmits data to the application program via the wireless access point and the communications server.

Abstract: A wireless classroom response system wireless network is located proximate to a classroom, a base station that coordinates the activities of the wireless network, and a plurality of handheld units. Each handheld unit is associated with an attendee of a class (either on a long-term or “owned basis, or on an ad-hoc or “shared” basis). Each handheld unit performs a discovery process that includes the steps of randomly choosing a wireless channel, attempting to discover the presence of the wireless network on the channel, and repeating these two steps if no wireless network is discovered.

Abstract: Presented is a modular uninterruptible power supply system utilizing common power modules, and providing redundant coordinated control thereof. The system and method of the instant invention provides identical control logic within each of the individual power modules, thus dispensing with the requirement for a separate control module to control and coordinate the operating modes and parameters of the UPS system. A system is presented whereby a virtual master is established through an arbitration scheme at initialization of the UPS system. The master then assigns a virtual vice master to provide the redundant back up control should the virtual master no longer be able to perform its functions. Nearly simultaneous control of operational mode and state change functions is accomplished through a coordinated communications system including a high-speed communications bus and digital control logic lines.

Abstract: A modular uninterruptible power supply is presented having multiple power modules installed therein. Each of the individual power modules contains an internal bypass circuit sized for its particular power module. Preferably internal bypass circuitry is sized to carry two per unit load. The system and method of the invention also includes internal control circuitry for each of the modular power modules that control transitions between the inverter and bypass modes of operation. This transition control is coordinated with the other controllers for the other modular power modules installed in the uninterruptible power supply. Both the high speed communication bus and a high level interrupt line are utilized to minimize the transfer break time between different modes of operation while ensuring that the inverter is never paralleled with the utility line voltage. To further minimize this transfer time, a solid state switching circuit is utilized to provide the initialization between operational modes.

Abstract: A line-interactive single conversion uninterruptible power supply (UPS) utilizing a multiple tapped ferroresonant transformer and a square wave PWM inverter is presented. During normal utility line operation, the line voltage is not modified in any way, except for ferroresonant filtering and regulation. Tap control circuitry insures proper tap selection based on the utility input voltage. During tap transitions in utility out of specification operation, a second power source, such as an inverter, is operated to provide output power to the connected loads. The control of the inverter switching angles may be accomplished through a look-up table. This look-up table contains the converter pulse widths for monitored battery voltage. No output voltage feedback is required. Based on the inherent regulation provided by the ferroresonant transformer, the PWM control may be accomplished in course steps.