HVAC Control in the New Millennium.pdf - HVAC.Amickracing

Control Technology, Microelectronics and Nanotechnologymonthly fees for using the satellite network. The wireless modem systemputs all of the cost up front. Once the modem is installed, youown the radio network.Mountain Water installed EST’s ESTeem model 95 modem whichoperates in the 72- to 73- or 75- to 765-MHz very high frequency(VHF) bands. It uses 9600-b/s RF data rate and a 20-kHz channelspacing.A peer-to-peer configuration is used where the modem alsofunctions as a repeater. Any station that can hear a transmission receivesthe transmission. If this signal has the modem’s address, itprocesses the signal. If there is a repeat string attached, the modempasses it off along the system to the next modem. There is no needfor stand-alone repeaters.Evolving ConnectivityFor about 15 years, the typical mouse for a personal computerwas connected to the computer serial port and communicated oneway. The mouse measured signals from an opto-coupler, made a fewcalculations to smooth the motion, and sent three bytes of data overthe line. A microcontroller was integrated into the mouse design toallow communications via software.Under the Universal Serial Bus (USB) the mouse is classified asa Human Interface Device (HID) and must conform to a unified commandset for software configuration and control. This communicationis bidirectional. There must be a response to commands or the mousebecomes disabled.The mouse identifies itself with a unique identification code soit can accommodate multiple point devices connected to a single system.The mouse should also support error detection and recovery forthe reliable delivery of data. This fully connected protocol requiresthat the software be able to handle up to 35 errors between themouse and the host driver software.System connectivity requires the ability to automatically configurethe system for the user. If boxes are added or removed, the systemmust reconfigure itself without losing data during operation.The local device control must be accurately maintained while itresponds to the network. Error detection and correction on the net-©2001 by The Fairmont Press, Inc. All rights reserved.