This decoder will respond to a preselected 4-digit DTMF number. IC7 is a Radio Shack IC device (part #276-1303..
If we are speaking about professional Cell phone Jammers we are talking about this schematic below. First off all you should be very careful how to use this device. Its fully illegal and so the purpose I post this Circuit is only for educational and testing reasons. This type of device is being used by security for VIPS, specially at their limousines to avoid bomb triggering while the car passes from the target cell phone-bomb. Offcourse there are those who use it to make.....
Input 1 is used as a gating period, during which a single rising edge on input 2 will cause a logic 1 output-any other number, indicating non-identical frequencies causes a logic 0 output. ICla converts input 1 to a narrow pulse which initializes IC2 which forms a two-stage shift register clocked by input 2. On the first edge of input 2 a logic 1 appears on the output of IC2b and for all subsequent inputs a logic 0 is present. At the end of the gating period this output is.....
The swept-frequency oscillator offers an inexpensive source of discrete frequencies for use in testing digital circuits. In this configuration, the circuit generates an 80-second seguence of eight frequencies, dwelling for 10 seconds on each frequency. You can change the dwell time or the number of frequencies. Frequencies can range from 0.005 Hz to 1 MHz. The programmable crystal oscillators, PXOs, IC2 and IC4 can each generate 57 frequencies in response to an 8-bit.....
Integrated circuit Ul (a 555 oscillator/timer) is wired as a conventional pulse generator. The frequency of the pulse generator is controlled by potentiometer Rll. Resistor R2 puts areasonable limit on the highest speed attainable. The output of the pulse generator is fed to the common clock input of U2, a 74C175 quad D-type flip-flop. Each flip-flop is configured so that its Q output is coupled to the D input of the subsequent flip-flop. Information on the D input of.....
The incoming RGB inputs are terminated with resistors Rl, R2, and R3 and potentiometers RVl, RV2, and RV3. These provide input impedances of approximately 75 0. The presets should be adjusted to provide a maximum input of 1 V pk-pk into the MC1377. The inputs are ac-coupled into the encoder; the large value capacitor is required for the 60 Hz field component. The Colpitts oscillator for the color burst is formed around pins 17 and 18. About 0.5 V pk-pk should appear.....
This simple circuit can color the sound coming from your audio system. Clocking for the circuit is provided by an oscillator built from one quarter of a 4093 quad NAND Schmitt trigger. With the component values shown, it will run at about 5 Hz. The clock frequency is fed to the gain control, pin 8, of an LM386 amplifier. Tremolo is produced by varying the amplifier gain. A trimmer potentiometer can be put in series with R1, to easily experiment with different.....
For back-lit LCD displays, this supply will drive a lamp. LT1072 drives Ql and Q2, and a sine wave app..
This encoder can generate up to 19,683 codes from 9 address lines by detecting 1,0, or open circuit. To initiate the transmit sequence, pin 14 should be pulsed low. The encoder will now output on pin 15 a data stream representing the condition on each of the address/data pins in turn and then repeat the operation, so that two complete identical words are transmitted. If pin 14 is held low, the output will be continuous, otherwise two identical words are output for each.....
In applications where the period of the input pulses is uneven and the divider is required to cover a wide range of frequencies, the non-integer programmable pulse divider shown can be used. The purpose of the D-type flip-flop (IC2) is to synchronize the input signal with the clock pulse. When the clock pulse changes from low to high and the input is high, IC2 output goes high. Subsequently, IC3 resets to zero and starts counting up...
The circuit uses a four-bit latch (Ul). What makes the circuit sequential is that the set input of the first bit latch is tied..
This circuit provides a simple, low-cost crosshatch generator tor convergence and geometry adJUStments on color TVs. The generator is driven by two clocks, one for the horizontal drive, IC1ab, and one for the vertical drive, IC2ab. The clock outputs are applied to the two binary counters contained in IC5 which generate the line and field sync pulses and respective blanking periods. Line clock pulses, buffered by IC1c, are differentiated by C3/R5 to produce the vertical.....
This circuit was used to produce a variable negative voltage for contrast control of an LCD displa..
The CD4069 or 74C04 hex inverter—is used as^ fixed-frequency oscillator centered around 100 kHz. U2 contains the variable frequency oscillator and balanced modulator. The CD4046 is a phase-locked loop and R3, R4, and C2 determine the center frequency of the on-chip oscillator. The antenna forms a parallel capacitance with C2, which allows the frequency to be shifted several kilohertz by bringing a hand near the antenna. R4, the ZERO control, allows the variable.....
This circuit draws only 4 mA from a 5-V supply while driving a standard RS-232C receiver. The system clock drives a de-de converter that produces -3.4 V. The frequency can range from 0.5 to 8 MHz, but a range of 0.5 to 1 MHz will minimize power dissipation. The circuit output withstands direct shorts to ground or to either of the supplies ( ±12 V max). ..
This filter is used to reject or block a frequency or band of frequencies. These filters are often designed into audio and instrumentation systems to eliminate a single frequency, such as 60Hz. Commercial grade components with 5%-10% tolerance produce a null depth of at least 30 to 40 dB. When a twinT network is combined with a TL081 op amp in a circuit, an active filter can be implemented. The added resistor capacitor network, R2 and C2, work effectively in parallel.....
In this proximity detector an NE567 tone decoder provides a signal of about 100 kHz that is fed to one sensor. The senso..
The sensing circuit rapidly disconnects the battery voltage and load whenever the voltage drops below a preset threshold. One-way operation prevents the circuit from reconnecting the load if the voltage should then rise above the threshold. Cl ensures that the circuit doesn"t activate while making connections to the battery; if you accidentally reverse these connections, Dl will block the turn on the relay. After you connect the battery, nothing happens until you.....
This simple cpo uses the 7404 low-power Schottky hex inverter. C is a 5- to 30-µf electrolytic selected for the desired pitch..
You can turn any ordinary household bulb into one that shimmers or blinks. This circuit works on any incandescent light up to 200 W, arid runs on standard 120 Vac. The circuit uses an SCR to cause an ordinary lamp to sliimmer. Note that one side of the lamp is connected directly to 120 Vac, and the other side of the lamp goes to the cathode of the SCR. As ac voltage is brought into the circuit through the line cord, it is full-wave rectified by diodes D1 and 1)2. That.....
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ANSI Standards
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