|
|
Relay
A relay is an electromechanical switch that uses an electromagnet to open or
close one or many sets of contacts.
When a current flows through the induction coil, the resulting magnetic
field attracts an armature that is mechanically linked to a moving contact.
The movement either makes or breaks a connection with a fixed contact. When
the current is switched off, the armature is returned by a spring to its
resting position.
Applications
Relays are used:
* to control a high-voltage circuit with a low-voltage signal, as in some
types of modem,
* to control a high-current circuit with a low-current signal, as in the
starter solenoid of an automobile,
* to isolate the controlling circuit from the controlled circuit when the
two are at different potentials, for example when controlling a
mains-powered device from a low-voltage switch.
A relay can be made into a buzzer by wiring up the coil in series with the
normally-closed contacts. When a current is applied to the relay, it opens
the contacts that provide current to the coil, causing the current to stop
flowing and the contacts to close again. This cycle repeats continuously,
causing the relay to buzz at an audible frequency.
Types of relay
A changeover relay has one moving contact and two fixed contacts. One of
these is normally closed when the relay is switched off, and the other is
normally open. Switching the relay on causes the normally open contact to
close and the normally closed contact to open.
A latching relay is mechanically arranged so that the armature can rest in
either of two positions. There are two coils that pull the armature in
opposite directions, so the relay can be switched to one position or the
other and then left in that state indefinitely. This type of relay has the
advantage that it consumes power only for an instant, while it is being
switched.
A reed relay has two, usually normally open, contacts inside a glass
envelope. This protects the contacts against atmospheric corrosion.
This content from Wikipedia is licensed under the GNU Free Documentation License.
|
NEW P4 2.8GHz 256MB DDR 80GB CDRW AGPNEW P4 2.8GHz 256MB DDR 80GB CDRW AGP ** NEW P4 2.8GHz 256MB DDR 80GB CDRW AGP **This FAST system features an Intel Pentium 4 2.8GHz processor, an 80GB 7200RPM hard drive, 256MB DDR RAM, and sports a 52x32x52 CDRW drive. It also includes a high powered GeForce MX4000 64MB AGP Video Card for great graphics!General Features:- Intel Pentium 4 2.8GHz Processor- 256MB DDR Memory- 80GB 7200RPM IDE Hard Drive- 52X32X52 CDRW Drive- Nvidia GeForce MX4000 64MB AGP Video Card- AC97 Integrated Audio- 56K V.90 Data/Fax Modem- Integrated 10/100 Ethernet- Standard Size ATX Power SupplyMotherboard Features:- Intel845D (Northbridge) / Intel ICH2 (Southbridge) Chipsets- One (1) 4X AGP Slot (Occupied by AGP card)- Five (5) PCI slotsI/O Ports:- Two (2) PS/2 Ports, one for mouse, one for keyboard- One (1) Standard DB-15 VGA Connector- One (1) Standard 25-pin Parallel Port Connector- One (1) Standard 9-pin Serial Port Connector- Six (6) Standard USB 2.0 Ports (Two on front, four on rear)- One (1) Standard RJ-45 10/100 Ethernet Port- Line-in, Phone-out RJ-11 Jacks on PCI Modem- Line-in, Mic-in, Line-out 3.5mm mini-jacksPackage Includes:- Eureka P4 2.8GHz System- PS/2 Keyboard and Scroll Mouse- Driver Disc- Panda AntiVirus Software- FaxTalk Communicator Software- Adobe Reader- RJ-11 Phone Cable for Modem- Amplified Stereo Speakers - Asrock P4I45D Motherboard manual- U.S. Style Power CordCompatibility/Requirements/Disclosures:** Requirements *** Operating system (WinXP,2000,98,etc.)* VGA monitor* Power outlet More ...
Professor Teaches Windows 2000Professor Teaches Windows 2000 Whether you're new to computers or just new to Windows 2000, this is the complete multimedia training program you need! Follow a comprehensive eight-chapter tutorial including hundreds of practical exercises designed to build essential skills in quickly and easily. This the easy, interactive way to learn Windows 2000! Windows 95/98/2000/ME/NT4/XP More ...
Lan Party Pack 5-Color Patch CablesLan Party Pack 5-Color Patch Cables ** Five Pack Multiple Colors 15-Foot Cat5e Cable **This multipack of five uniquely colored cables is perfectfor your customers who are building or repairing a network.This CMR rated cable pack is ideal for installation inhouses and offices and is suitable for use in risers. Thiscomes packaged in a plain box.General Features (per cable):- 15 foot length- Category 5e - Suitable for Gigabit Ethernets- (Also works great in 10BaseT and 100BaseTX environments)- UL Approved- CMR (Riser) Rated*- 24AWG Stranded Copper Conductors - Four (4) Unshielded Twisted Pairs (UTP)- RJ-45 Connectors at both ends with moulded-in Strain ReliefsPackage Includes:- One (1) White 15-foot Category 5e cable- One (1) Blue 15-foot Category 5e cable- One (1) Green 15-foot Category 5e cable- One (1) Orange 15-foot Category 5e cable- One (1) Yellow 15-foot Category 5e cableNotes:- CMR (riser): Cables may be used to penetrate floors and ceilings in vertical shafts. May not be used in air handling spaces. Compatibility/Requirements/Disclosures:** Requirements *** Basic Networking Knowledge* Ethernet Hub and Computer with RJ-45 Ethernet Port More ...
HP P4 2.8GHz 512MB 160GB DVD+RW CD XP Media CtrHP P4 2.8GHz 512MB 160GB DVD+RW CD XP Media Ctr ** HP m377n Pentium 4 2.8 GHz Media Center PC **This Hewlett Packard m377n lets you enjoy multi-media entertainment as well as do your basic computing functions! It features a fast Intel Pentium 4 2.8 GHz processor with Hyper-Threading technology and 512 MB of RAM. The 160 GB hard drive is pre-loaded with Microsoft Windows XP Media Center Edition. A DVD+RW/CD-RW combination drive lets you create CDs, DVDs, and watch DVDs. Transfer files, photos, or data with the 7-in-1 memory card reader. Access the Internet through the PCI modem or the integrated 10/100 Ethernet controller. USB and FireWire ports are built-in to connect your high speed devices like cameras, scanners, camcorders, or printers. A keyboard, mouse, speakers, and remote control are included with this Hewlett Packard m377nMedia Center PC!General Features:- Microsoft Windows XP Media Center Edition pre-installed- Intel Pentium 4 2.8 GHz processor w/Hyper-Threading technology- 512 MB DDR RAM (2 GB maximum)- 160 GB hard disk drive- DVD+RW/CD-RW combination drive- CD-ROM drive- 1.44 MB floppy disk drive- 7-in-1 memory card reader- AGP video card - Integrated audio- TV Tuner PCI card- Integrated IEEE 1394 FireWire- 56K PCI modem- Integrated 10/100 Ethernet controllerSupported Media:- Compact Flash I/II- Memory Stick- Memory Stick Pro- Microdrive- Multimedia- Secure Digital- Smart MediaFront Panel Media Shortcut Buttons:- TV Window button- Program Guide Button- Music Window button- My Pictures Window button- My Videos Window buttonMotherboard Features:- One (1) AGP slot (occupied)- Three (3) PCI slots (two occupied)- Four (4) 184-pin DIMM slots (two occupied)I/O Ports:- Two (2) PS/2 ports- One (1) 15-pin standard VGA connector- One (1) 9-pin standard serial port- One (1) 25-pin standard parallel port- One (1) Composite out- One (1) Composite video input at front- Two (2) S-Video in (one on back and one at front)- One (1) S-Video out on back- One (1) FM in- One (1) TV connector in- Left and right audio inputs (front and back)- Six (6) USB 2.0 ports (four on back and two at front)- Two (2) IEEE 1394 FireWire ports (one on back and one at front)- One (1) RJ-11 standard phone jack- One (1) RJ-45 standard Ethernet jack- Line-in, microphone, and line-out jacks on back- Microphone and headphone jacks at frontCase Features:- Two (2) 5.25-inch external drive bays (occupied)- Two (2) 3.5-inch external drive bays (occupied)- One (1) 3.5-inch internal drive bay (occupied)- 200-watt power supply (100-240V, 47/63Hz)Case Dimensions:- 15.5 x 8.25 x 15-inches (H x W x D)Regulatory Approvals:- UL- FCCPlain Box Includes:- HP m377n Pentium 4 2.8 GHz Media Center PC - Microsoft Windows XP Media Center Edition pre-installed- User's Guide- Remote control- USB remote sensor- HP PS/2 Multimedia keyboard- HP PS/2 3-button scroll mouse- Harmon Kardon Subwoofer w/AC adapter (120VAC, 60Hz)- Two (2) Harmon Kardon Speakers w/AC adapter (120VAC, 60Hz)- Phone cord- Power cordNotes:- Windows and driver CDs are not included.- Two (2) AA batteries for remote are not included Compatibility/Requirements/Disclosures:** Requirements *** VGA monitor* AA batteries for remote control* Available power outlet More ...
Intel Celeron 266MHz 66MHz Slot 1 CPUIntel Celeron 266MHz 66MHz Slot 1 CPU ** Intel Celeron 266MHz 66MHz Slot 1 CPU **Getgreat performance for your personal computing and the quality and reliability you expect from the Intel Inside brand with Intel Celeron processors for desktop PCs.General Features:- Intel Celeron 266MHz- Slot 1 SEC- MMX instructions set- CPU Only (Heatsink and Fan NOT Included)Compatibility/Requirements/Disclosures:* Motherboard that supports Celeron 266MHz CPUs* Celeron Slot 1 SEC Heatsink & Fan More ...
Batsonic Agere 56K V.92 PCI Data/Fax/Voice ModemBatsonic Agere 56K V.92 PCI Data/Fax/Voice Modem ** 56K PCI Data Fax/Modem with Agere Chipset **Connect your computer to the world with this Agere-based PCI modem! With download speeds at 56Kbps using the v.92 standard, you'll be getting data as fast as the phone lines can provide it! Even if you use broadband, it's worthwhile to have a modem for those times when the network is down and you absolutely have to connect! Plus, you can use this modem to fax your documents!General Features:- Agere SV92PL-T00 soft chipset- 56K modem- v.92 ready- PCI interface- Hayes AT command compatible- Supports voice function/TAM- Supports video conferencing (H-324)- v.17, v.29, v.27ter Group3 fax support- v.42bis/MNP5 data compression- v.42/MNP2-4 error correction- Voice/TAM- H.324 video phone ready- Class 1 fax command set- Auto diagnosticsRegulatory Approvals:- FCC- CERetail Package Includes:- 56K v.92 ready data fax/voice modem- Driver disc- RJ-11 standard phone cord Compatibility/Requirements/Disclosures: ** Requirements *** Microsoft Windows 98SE/NT 4.0/2000/ME/XP* Intel Pentium 166 MHz MMX processor or faster* 20 MB free hard disk space* Sound card for voice features* Avaialble PCI slot* CD-ROM drive for driver installation More ...
|
