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The particular circuit combines enough operations, as: [ 1 ] Smooth departure of benefit of AC line of network, with delay 1sec, to the transformers of power supply of amplifier, via the RL1 and the resistance Rx. (see block diagram). [ 2 ] Delay of connection of expenses of final amplifiers, in headphone, in order that noises emanating from the charge - uncharged of capacitors of power supply, they do not pass in them. Simultaneously becomes control of exit of amplifiers for existence of continuous voltage [DC]. If all go well it connects, the amplifiers in loudspeaker.... [read more]

When this alarm is activated its Siren will sound once - for up to 20-minutes. Then it will switch off and remain off. The basic circuit has a single zone with independently adjustable Exit and Entry delays. This will be adequate in many situations. However, there's also a range of Expansion Modules. These will allow you to add any number of Instant Zones, Tamper Zones and Personal Attack Zones to your system.... [read more]

The two circuits illustrate generating low frequency sinewaves by shifting the phase of the signal through an RC network so that oscillation occurs where the total phase shift is 360 degrees. The transistor circuit on the right produces a reasonable sinewave at the collector of the 3904 which is buffered by the JFET to yield a low impedance output. The circuit gain is critical for low distortion and you may need to adjust the 500 ohm resistor to achieve a stable waveform with minimum distortion. The transistor circuit is not recommended for practical applications due to the critical adjustments needed.... [read more]

Men in particular enjoy the convenience of television remote controls – often to the annoyance of their female partners. Men apparently want to know what they’re missing when the TV is tuned to a particular program, so they like to keep zapping to other channels. With the remote control in their hands, they feel like they are the lord and master of the TV set. They are thus completely at a loss if the remote control doesn’t work properly. There are many reasons why a remote control unit can malfunction, such as defective IR receiver in the TV set, a defect in the remote control, or empty batteries. Here a tester that can determine whether the remote control unit still emits an IR signal can come in handy. If you want to keep the IR reins firmly in hand, you can build your own IR detector.... [read more]

This circuit is suitable to amplify and distribute the audio signals. The input audio signal is applied to the J1 and after passing through the P1, It is buffered and amplified by the IC1 prepared to redistribute. It has 3 outputs to drive 3 audio lines with 300 ohms impedance.... [read more]

The ckt is built around two 555 timer ICs. U1 and U2. U1 is wired as a variable duty cycle oscillator with a constant time period of around 0.1 second. Duty cycle can be varied from 0 to 100 per cent by R4 potentiometer. The output of U1 (pin 3) is connected to the rest input (pin 4) of U2.... [read more]