AC IR Remote Control -  This RF remote control it runs at 418 MHz frequency and support up to 2 channels.  It is very safety as the transmitting code is changing every time you push any button   (roll-code function)___ © Vassilis Serasidis

Device Control using DTMF -  Controlling devices using switches are common.  From a few decades controlling devices using remote control switches like infrared remote control switch, wireless remote control switches, light activated switches are becoming popular.  But these technologies have their own limitations.  Laser beams are harmful to mankind.   __

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,__ Circuit Design by Criscuolo Anna Rita, Labtec Telecommunications, Nichelino, Italy

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 Bob Blick

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

Radio Remote Control using DTMF -  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

Remote control using telephone -  Here is a tele-remote circuit which enables switching "on" and "off" of appliances through Telephone lines.  The circuit described here can be used to switch up to nine appliances (corresponding to the digits1 through 9 of DTMF the Telephone key-pad).  The Telephone can be used to switch __

Simulate signals for telecomm tests -  9/11/98 EDN-Design Ideas NOTE : File has several circuits, please scroll to find this one.  The circuit in Figure 1  is a miniature gadget that is heLPFul in telecommunication applications.  The function of the device is to simulate data flow with predefined patterns and use these patterns to check a cable's or a receiver's functionality.  The circuit generates a signal in accordance__ Circuit Design by Samuel Kerem, Patton Electronics, Gaithersburg, MD

Duel Tone Multi Frequency (DTMF) Circuits