Decoder Circuit

Telephone DTMF decoder Display

The given circuit, when connected in parallel to a telephone, dis- plays the number dialled from the telephone set using the DTMF mode. This circuit can also show the number dialled from the phone of the called party. This is particularly helpful for receiving any number over the phone lines. The DTMF signal generated by the phone on dialling a number is decoded by DTMF decoder CM8870P1 (IC1), which converts the received DTMF signal into its equivalent BCD number that corresponds to the dialled number. This binary number is stored sequentially in 10 latches each time a number is dialled from the phone. The first number is stored in IC5A (1/2 of CD4508) while the second number is stored in IC5B and so on...

MS Decoder schematic

The schematic diagram of the MS Decoder may look complicated but is actually quite simple. Both the Mid and Side signals are initially buffered by unity gain inverting buffers formed around IC1b and IC2 b. This is necessary for two reasons, first to ensure enough drive current for the following sections. Second, the final summing sections invert the signal, to achieve zero phase shift through the unit, one more stage of phase inversion is required. The Mid signal goes to level control potentiometer R15. It is then fed equally to the left and right summing amplifiers, which are formed around the two sections of IC3...

7-segment display with encoder

This design explains how to use an encoder to set the number shown by a 7-segment display. Turn the knob clockwise to increment the number, turn it counterclockwise to set it back. Encoders are the most practical (and handy) way to set a large number of digital devices. Think of an alarm clock, would'nt be easier to set the alarm time simply turning a knob, in place of frantically pressing a couple of buttons? By the way, grandma alarm clock works exactly in that way. The circuit counts four main parts (Nutchip, encoder, display driver and display), nonetheless should not be difficult to understand. Its a matter of connecting two Nutchip inputs to the two encoder pins, and all four Nutchip outputs to a 4511 7-segment display driver. ..

Telephone Hold Line

The UNIVERSAL HOLD circuit detects the dual tone, multi frequency (DTMF) tone that is generated when the # key is pressed and then activates a circuit that partially loads the telephone line so that the central office thinks a phone is still off hook even after it is hung up. When any phone is again picked up, the hold function is canceled...

Video Camera switcher MAX454

The video switcher described here can display the output of two, three, or four cameras on a single monitor. The number of cameras is set by a DIP switch on the circuit board. That feature avoids blank displays if less than four cameras are used by sequencing through only the inputs that are connected to a camera. In the automatic mode, the cameras are switched at a rate that can be varied with a panel mounted control. The switching rate can be set from about once per second to about once every 20 seconds. In the manual mode, one camera output is displayed continuously. A momentary-toggle switch is then used to step through the various cameras. The heart of the video switcher is a Maxim MAX454...

DTMF decoder with voice!

The Talking Phone Dial Monitor detects the tones generated when numbers are dialed on your touch tone telephone and speaks the numbers that were dialed. This verifies that you dialed the correct number and is especially useful when the keypad is not well lighted or if the person dialing cannot see the keypad well for any reason. The numbers that are spoken can be prerecorded by speaking into a built-in microphone and can be re-recorded at any time if desired...

IR Encoder/Decoder with PIC12C508

The receiver chip uses a Panasonic 4602 38KHz receiver and that's it for external components. It has the serial input (GP3) , two RC hobby servo outputs (GP0/GP1) and three digital outputs (GP2,4,5). Here is the code for the receiver chip. It is a bit of a specialty in that the digital outputs are actually "momentary contact" type outputs because I only needed a pulse to go out to trigger a cheap sound board I got from a $6 toy! I don't even use the GP2 output in this design. The receiver uses 4 NiCd 115MAH cells, the largest set I could fit into the Rhino! The transmitter chip uses 5 pullup resistors and an IR LED powered through a 330 resistor - quite a bit of power I think. To keep things simple, I used a 78L05 to power the PIC so I could use a 9V battery and keep the whole project box size small. It will run fine on 3 alkaline cells, or, from 4.5 to 5.5V. ..

Surround Sound Decoder

The particular circuit does?t have the requirement to replace the trade decoders Surround, because this they have many more facilities and possibilities. It give however the possibility in many try with this article of decoding. The coding in Stereo Dolby Surround show the tendency to be abandoned and is replaced with digital DTS, Dolby 5.1 etc, that is supported in the digital level of management and transport, sound signal. In order that appears also in the Fig.2, the stereo sound signal that transport the surround information, is drive for the Lch in the IC1A and Rch in the IC1B, that is input buffer with the next stages. ..

Digital Encoder with PIC16F57

This encoder can transmit the state of up to 16 TTL digital inputs using an RF or infrared transmitter. When enabled, the included modulator automatically generates the 38kHz IR carrier. Containing a PIC microcontroller, the circuit is very flexible. You can decide which transmitter inputs will trigger a transmission. You can control the receiver outputs to be latched or momentary with the LATCH input. The Manchester-coded transmitter output is well suited for the cheapest ASK radio modules or for infrared control. Address decoding is not yet supported. If you have trouble with programming PIC microcontrollers, you can consider builing other circuits based on Holtek HT-12D, HT-12E and Motorola MC145026, MC145027, MC145028 encoders/decoders...

CW Decoder using PIC16F84

The device is equipped with a 2x16 LCD display , the text shifts from left to the right starting from the end of the second raw. An inter-words automatic spacing function is provided, based on a regular timing of the pauses in the sent code. This function may be inhibited grounding the J pin if the device is used for training purpose or while receiving an improperly sent code. The audio input must be at least 100 mV pp, a clipper is provided to cut large signals. The band width is about 100 Hz and the center frequency may be adjusted between 700 and 1000 Hz by a trimmer...

This is a simple surround sound decoder. Left & right outputs of a stereo tape or CD player can be connected to the circuit inputs and 4 outputs of the circuit can be connected to a surround power amplifier or 2 stereo power amplifier. ..

The signal output by the radio control receiver is a form of PWM. This may be useful for driving servos, but is inconvenient for general electronic applications. Therefore, several of the circuits on this site convert this signal into a voltage first. This is performed by this circuit. It is not a project in its own right, just a building block used by other projects. First we must see what these signals look like. There is a document here which describes servo signals in some detail, but Ill reproduce the timing diagram here for simplicity...

Decoding this bit stream into ASCII hex values is an ideal job for a low-cost 8-bit microcontroller. Using a microcontroller with onboard flash memory, such as the NEC Electronics µPD78F9418A (www.necelam.com), eliminates the need for external memory. The only external components are a few discrete devices for the signal detector and the coaxial-cable loop-through (Figure 2)...

The HT-12E is a CMOS IC. This encoder serially transmits data as defined by the state of the A0 to A7 and D0 to D3 input pints. On power-up, the DOUT pin is low. The HT-12E begins a 4-word transmission cycle on receipt of a transmission enable, or TE, signal, which is active low. The cycle repeats as long as the TE signal is low. When TE goes high, the encoder completes its final 4-word transmission cycle and then stops (Figure 1)...

The decoder`s operation is more complicated than that of the encoder. A behavioral simulation (Figure 2) shows the internal signals that are involved in the decoding process. Note that the spike on the "cd" signal is not a true spike; it appears only in the behavioral simulation and disappears in postlayout simulation...