Basic Flashlamp Illumination Circuitry for Cellular Telephones/Cameras:  DN345 -  Design Notes (Linear Technology) (app note added 1/06)

BayComm packet modem:  (circuit / schematic added 6/05)

Caller ID Display Service:  Caller ID decoder based on 68HC11, text in French / (added 8/03)

Caller ID:  (circuit / schematic added 2/03)

Caller ID/DTMF Audio Decoder:  (electronic (schematic / circuit added 4/02)

Cell-Phone-Controlled Audio/Video Mute Switch:  (electronic Circuit / Schematic added 10/04)

Cellular Phone calling Detector:  Flashes a LED when detecting an incoming call.  Powered by one 1.5V cell (added 4/05)

Chip recorder customizes phone ringer:  07/25/02 EDN Design Ideas  /  (added 1/05)  Companies usually purchase one type of telephone for all employees, which is understandable, especially if they obtain a discount for buying in quantity. One ringer sound for everyone can pose a problem, though, if the sound of a ringing phone makes a dozen people pause and look at their telephones. Equally annoying is the absence of a visual message indicator....

Circuit Provides Message on Disabled Phone Line:  01/20/00 EDN-Design Ideas / (added 5/02) / This circuits plays a prerecorded message into any phone on the line when its receiver goes off-hook

Circuit to Connect Telephone Equipment to Audio Mixer:  I have used this type of circuits for quick testing of telephone equipment. This is a quick hack that does not exactly resemble the characteristics of the real telephone network, but is enough for this kind if applications. If you want better simulation, change the resistor to 600 ohm and increase the power supply voltage. And by the way you can also feed signals to telephone if you connect the circuit output wires to small amplifier output. (added 6/06)

Circuit Translates a Law to µ Law:  05/07/98 EDN-Design Ideas / (added 3/03)   -- Two common methods exist to command voice for transmission through a PCM channel

Circuit Vocalizes Telephone Number:  02/03/94 EDN-Design Ideas / (added 3/03) The circuit in Fig 1 is a simple method of vocalizing the digit number of a telephone keypad, which, for someone visually impaired, provides helpful voice confirmation. A 75T202 dual-tone multifrequency (DTMF) receiver decodes the DTMF signal when you depress the phone's keypad. The TC8801N voice synthesizer outputs the voice data corresponding to the data input code. A TA7368P audio power IC amplifies the result. The logic gates perform necessary code conversion for the voice-synthesizing IC's input. (DI #1357)....

Circuitry for Cellular Telephone/Camera Flash Illumination:  AN95 - Linear Technology - This publication concerns implementation of high quality "Flash" illumination in cellular telephones/cameras. Performance vs LED based illumination is discussed and flashlamp operation reviewed. Considerations for support circuitry are given, and a practical circuit, accompanied by performance data, is described. Layout and RFI issues are treated and a sample layout provided. An appended section details operation of the LT3468 flash capacitor charger used in the text's circuit and lists appropriate magnetic components.

Clip extracts signal from phone line:  07/24/03 EDN Design Ideas  /  (added 1/05)  Using a capacitive-coupled clip, you can pick up the signal from a twisted-pair or -wire telephone line or from other unshielded analog lines without piercing the insulation. No line test can detect the clip's presence, and it leaves no evidence of having been attached. It needs no ground return. You can fasten the small, insulated pickup plates to the opposing jaws of an alligator clip for qui......

Connecting a Picmicro® Microcontroller to a Standard Analog Telephone Line:  Microchip Application Note - Published 21-Aug-02   (app note added 6/06)

Conversation Recorder:  (electronic circuit added 10/05)

Cordless Phone Backup #2:  (electronic Circuit / Schematic added 10/04)

Cordless Phone Backup:  (electronic circuit added 10/05)

Creating your Own Telephone Ne2 Rk:  you can easily create your own intercom system using two telephones, a 9-volt battery (or some other simple power supply) and a300-ohm resistor (added 5/02)

Cut Phone Line Detector #1:  Can be used to alarm security system (added 5/02)

Cut Phone Line Detector #2:  (electronic (schematic / circuit added 4/02)