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This is a simple circuit that activates an alarm when there is a knock on the door or there are any vibrations due to movement of heavy goods or furniture. The circuit uses readily available components. Circuit and working The circuit is built around quad-opamp LM324 (IC1), which is configured in amplifier mode. It uses the piezoelectric element of a piezo buzzer as the input sensor, two transistors BC547 (T1 through T2), a piezo buzzer and some other components for the alarm circuit. Fig. 1 shows the circuit diagram of the door-knock alarm. The reference voltage at pin 3 of IC1 is set by trimming potmeter VR1. The piezoelectric element plate is fixed at the centre of the door using cello tape. Apply a small quantity of adhesive on the edges between the plates. Wires from the piezo element are connected at CON2. These generate an input pulse when vibrations are caused by knocking on the door. The pulse is amplified by op-amp A1 of IC1. Remaining three op-amps of quad IC LM324 are not u...

If users don't update their Windows Phones to 7.5, they won't be able to access Marketplace. (Credit: Josh Miller/CNET)    Anyone with a Windows Phone that hasn't been upgraded to version 7.5 won't be able to use Microsoft's Marketplace app store as of today. Microsoft announced today that in order to download, buy, update, or review apps in Marketplace, users have to be running Windows Phone 7.5. This change is required for both the phone and web Marketplace storefronts. "Most phones are already running Windows Phone 7.5, which was released last fall, and so most of you won't notice anything different about how the Marketplace works," Microsoft's director of program management, Mazhar Mohammed, said in a blog post today. "However, if your phone has an earlier version of our software installed, you'll soon start seeing an error message when you try to download a new app, or update one you already own."

This is a simple design, can have excellent results, he is a recipient of regeneration, if you have never built any receiver, this is one you will build Easy. The circuit described is simple and has many limitations in sensitivity and selectivity, but is able to receive signals from radio amateurs (40m or 80m) in SSB and CW, and as output using a small headset crystal.  He will have a saturation if there are strong stations available on AM broadcast band of 41m at night.L1 is a small toroid T50-2 (red) with about 18 to 20 times (40m) or 35 to 40 times (80m) in the main winding connected to the FET with a single coupling circuit facing the antenna connection.  The center tap is about 20% of the primary winding. C1 is adjusted to set the radio band to the 40m and C2 then acts as a fine tuning within the band.The supply of 12 to 14V, R2 should be increased 5K6 or 6K8 output will be higher and similar sensitivity to-100dBm (about 2uV). Regenerative Receiver Circuit Diagram

If users don't update their Windows Phones to 7.5, they won't be able to access Marketplace. (Credit: Josh Miller/CNET)    Anyone with a Windows Phone that hasn't been upgraded to version 7.5 won't be able to use Microsoft's Marketplace app store as of today. Microsoft announced today that in order to download, buy, update, or review apps in Marketplace, users have to be running Windows Phone 7.5. This change is required for both the phone and web Marketplace storefronts. "Most phones are already running Windows Phone 7.5, which was released last fall, and so most of you won't notice anything different about how the Marketplace works," Microsoft's director of program management, Mazhar Mohammed, said in a blog post today. "However, if your phone has an earlier version of our software installed, you'll soon start seeing an error message when you try to download a new app, or update one you already own."

Ladder Logic for AND ,OR, EX OR, NAND ,NOR Gates with Truth Tables   Following table shows symbol ,truth table and Ladder diagram for AND ,OR, EX OR, NAND ,NOR Gates.