Universal 4 Digit Keypad Operated Switch -  I've modified the design of the output section - to free up the relay contacts. This allows the circuit to operate as a general-purpose switch. I used a SPCO/SPDT relay - but you can use a multi-pole relay if it suits your application. . .  [Circuit designed by Ron J]

Universal DC Sink to Source Converter -  As illustrated below, many control systems use an open collector transistor to turn something on. Perhaps it is a LED light, a relay or a small motor. However there are other  systems which require a common ground connection instead of a common V+ supply . . . [Hobby Circuit designed by David Johnson P.E.,  03/27/11]

Universal Telephone Hold -  Place any phone in your house on holdeven cordless phones. 7 pages. Not available as a kit of parts. . . .  [free circuit from Golab.com]

Up/Down Ramping Light Pushbutton Control -  There are times when you want a lamp to gradually change from dark to light and from light to dark, with each push of a pushbutton switch. The circuit below performs this control function using a flip/flop and a classic pulse width modulation or PWM . . . [Circuit by David A. Johnson P.E.,  03/22/09]

USB Printer Sharing Switch -  I had two computers, a Mac Mini and a generic Windows computer. Both were on different networks, but in the same room, and I wanted to share a Lexmark USB laser printer between the two of them. I ended up making this switch to share the printer between the two computers. . .  [From Dick Cappels' project pages]

USB switch -  You can connect one USB device like a printer or scanner on 2 computers and controlled by software. . . 

Using model PSW-1201 as a SPST switch -  AN-80-001Application Note. . .  [MiniCircuits.com]

Using the RSW-2-25P switch -  AN-80-004Application Note. . .  [MiniCircuits.com]

VGA Switch -  Digital VGA switch for switching between two PC monitors with MAX465 IC. . . 

Video Routers -  VISW 8 x4 Stereo audio/video router. . .  [Mijo Kovacevic, S51KQ]

Video Switcher -  Automatically or manually switch the outputs from up to four cameras into one video monitor. 8 pages. Not available as a kit of parts. . . .  [free circuit from Golab.com]

Video switcher -  Monitoring several cameras on one monitor is usually done in one of two ways:  divide the screen into sections and show them all at once, or time sequence the cameras onto the whole screen. . . .  [by Luhan Monat-Mesa Arizona]

Video Switcher -  Monitoring several cameras on one monitor is usually done in one of two ways: divide the screen into sections and show them all at once, or time sequence the cameras onto the whole screen. This device uses the second method (which, if you don't already know, . . . .  [Luhan Monat - Mesa Arizona]

Voice activated switch -  The VS-1 provides quality components and a compact printed circuit board that makes it a snap to turn on a multitude of devices, from HAM transmitters and amps to tape recorders or clandestine listening equipmentHAVE FUN!. . . 

Voice-Over Circuit -  switches automatically from sound source to microph1-when enough sound comes in from microph1. . .  [Andy Collison's website]

Voltage Comparator Switch -  This circuit will provide an indication whenever the input voltage differs from two defined limits, V1 and V2. The supply voltage, VCC must be higher than the highest input voltage by at least 2 volts. One application here is to monitor a 12V car battery. . .  [Andy Collison's website]

Voltage Controlled Switch using 555 -  In this circuit the 555 timer is used in a novel way, as a voltage controlled switch. . . .  [Circuit designed by Miroslav Adzic]

Voltage-Based Controller for Switches -  . . . 

Vxi Switching Application Note 5968-7234 -  Application Note. . .  [Aligent]

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