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DSL Filter (phone-line) - The above diagram is a standard low-pass telephone line filter (L1, C1, L3, C2). L2 and L4 are needed since we're dealing with the 'Tip' and 'Ring' of a phone line which may carry up to 90VAC! __ Designed by Tony van Roon VA3AVR
DTMF Coder Makes Low-Cost Sine-Wave Generator - 10/13/94 EDN Design Ideas: A telephone DTMF IC produces, by design, two tones if you connect a single intersection of the IC 's 4[x]4 keypad matrix (Fig 1]. (Telephones commonly have 3×4 keypads but, unknown to many people, the applicable standard allows for a fourth row of four keys. ]But, if you connect two key inputs at once, the IC produces a single-frequency, Design by Criscuolo Anna Rita, Labtec Telecommunications, Nichelino, Italy
DTMF Decoder - Uses MT8870 DTMF decoder and PIC microcontroller to decode telephone tones. __
DTMF Decoder for PC - Our DTMF decoder can be powered from a 9V battery or from your parallel printer port. it can detect and display all 16 DTMF digits on your computer screen in real-time. The Window's program can be placed in the minimize mode and still detect tones while you use your computer to do other things like Net surfing! ! ! ! We are now in the process of adding an DTMF decoder which will interface to the sound card gameport. __
DTMF Decoder with LCD Display - The DTMF decoder 2 is a useful tool used for decoding DTMF (Dual Tone MultI frequency) generated by telephones. The decoded digits are viewed on a 16x2 LCD screen. __
DTMF Generator/Decoder - The photo depicts a DTMF generator/decoder pair you can build in an afternoon or two. Dual-tone-multi-frequency (DTMF, also known as touch-tone) are the audible sounds you hear when you press keys on your phone. The tone generator (top) uses the 5589 chip and a DiP switch. You can actually hear the tones through the speaker. The bottom circuit uses the 8870 to decode a tone and display its associated number on the 7-segment LED. __ Designed by Boondog web site
DTMF Radio Remote Control - Here is a circuit of a remote control unit which makes use of the radio frequency signals to control various electrical appliances. This remote control unit has 4 channels which can be easily extended to 12. This circuit differs from similar circuits in view of its simplicity and a totally different concept of generating the control signals __ Designed by Radioland.net
DTMF RECEIVER - Today, most telephone equipment use a DTMF receiver IC . One common DTMF receiver IC is the Motorola MT8870 that is widely used in electronic communications circuits. The MT8870 is an 18-pin IC . it is used in telephones and a variety of other applications. When a proper output is not obtained in projects using this IC , engineers or technicians need to test this IC separately. A quick testing of this IC could save a lot of time in research labs and manufacturing industries of communication instruments. Here’s a small and handy tester circuit for the DTMF IC . __
DTMF Tone Decoder - hears touch tones and displays them as telephone numbers __ Designed by Boblick
Dual Band Mobile Jammer for GSM 900 & GSM 1800 - Undergrad project, Dept Electrical Engineering , Jordan Univeristy of Science & Technology]__ Ahmed Sudqi Hussein Abdul-Rahman and Ahmad Nasr Raja Mohammad
Dual-voltage supply powers SIM card - 01/20/00 EDN Design Ideas: Global-system-for-mobile-communication phones have a subscriber-identification module (SiM) that allows local wireless providers to recognize the user and his or her billing information. Although most SiMs are changing to 3V operation, they also accommodate 5V as well during the transition. Design by Larry Suppan
Duo Phone - This simple circuit of a duophone allows you to access two telephone lines through one telephone set. Each telephone conversation will remain entirely separate unless you choose to combine the two...__ Electronics Projects for You
E10-G RS232 Modem - How to connect a PC RS232 moden to you Pocket PC__ © Vassilis Serasidis
Ericofon installation notes - To clear up facts about this trendy Ericsson telephone, as well as killing off the myth that these telephones do not contain a ringer. __ Contact blehack @ yahoo dot com
ErICsson Cell Phone Display GA628 - The GA628 display provides a 12 character alphanumeric display , some icons in the second line and power consumption of some 100 uA. it can easily be connected to the hardware, simply by soldering some wires. The only disadvantage is , it needs a 3.3 V power supply and something around 5.6V. However, this code and the MSP430 provides a clock for a simple charge pump, realized with 3 diodes __ Designed by Robert Tyrakowski
Extension Phone Line Switcher - Having multiple extension telephones at home is very convenient. You can make or receive phone calls practically anywhere in the house. This circuit disables other telephones connected to the phone line whenever a telephone (either the master or any extension phone) is in use. The circuit is inexpensive and is guaranteed to keep the phone conversation private. The circuit does not need an external power supply. it gets its power from the telephone line. __
Five band graphic equalizer - This circuit uses a single chip, IC BA3812L for realizing a 5 band graphic equalizer for use in hi-fI audio systems. The BA3812L is a five-point graphic equalizer that has all the required functions integrated onto one IC . The IC is comprised of the five tone control circuits and input and output buffer amplifiers. The BA3812L features low distortion, . __
FM bug 420-480 MHz - How about getting that old Nokia phone out of your drawer and turning it into something freakishly cool? I will not lie to you, you will need a few tools and skills such as soldering/desoldering and making PCBs. Here you can download Sprint-Layout__
FM Bug-transmitter - The circuit consists of two separate stages. The first is an audio pre-amplifier and the second is a 90MHz oscillator. The first stage is very simple to explain. it is a self-biasing common-emitter amplifier capable of amplifying minute signals picked up by the electret microphone __ Contact kit is designed and manufactured TALKING ELECTRONICS
FM Telephone Bug - Receive telephone conversations on any FM radio with this neat little device. __ Designed by Tony van Roon VA3AVR
FM Telephone line Bug Transmitter - Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can be tuned from 88 to about 94Mhz and the range is about 200 feet. it is extremely easy to build and is therefore a good, useful beginner project. __ Designed by Aaron Cake
FM telephone line bug transmitter (88MHz to 94MHz) - Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can be tuned from 88 to about 94Mhz and the range is about 200 feet. it is extremely easy to build and is therefore a good, useful beginner project. __
FM Telephone Transmitter - Receive telephone conversations on any FM radio with this neat little device. __ Designed by Tony van Roon VA3AVR
Four ICs implement video AGC & DC restore - 06/18/98 EDN Design Ideas: Four IC s--a multiplier, a sync separator, an op amp, and a dc-restore IC --along with a handful of passive components can implement a complete AGC and dc-restore circuit for video signals (Figure 1). The circuit consists of three main paths the signal path, the gain-control path, and the dc-restore path. The input video signalFile contains several Design ideas, scroll to this one Design by Tamara Ahrens and Mike Wong, Elantec Semiconductor Inc, Milpitas, CA
Four Line Telephone Line Status Indicator - Many home businesses use multiple phone lines. This circuit gives you a visual indication when a line is in operation. The two AA battery cells should provide enough power for about one year of operation. . . Circuit by Dave Johnson P.E.-June, 2000
Fourth-Order Speech Filter (Based On Texas Instruments Application Note) - Human speech generally occupies an audio spectrum of 300 to 3400 Hz. There is a requirement, especially in telephone circuits, to limit the frequency response to this range. The ‘Digital Speech...__ Electronics Projects for You
FSK Modem with PIC16C84 - schematic only __ Designed by shaunwilson19 @ yahoo.com
Full-duplex doorphone with 3 Wires connection - This circuit is a two-way (full-duplex) construction planned for use as door phone. To use, two pieces of the same circuit must be connected together with three wires: MiNUS (ground) , PLUS (power) and LiNE. One of the circuits must be connected to a stabilized power supply, 6-30VDC __ Designed by Peter Jakab |
