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Telephone Circuits

Telephone Circuits:   #'s - B       C - F       G - K       L - Q       R - S      T - Z
 

Last Updated: October 24, 2017 02:55 PM

Circuits Designed by Dave Johnson, P.E. :

Cell Phone Charger -  It seems that as cell phones become more sophisticated, their operating times become shorter and shorter.  If you are on the go all the time and have difficulty finding AC or DC outlets to charge your phone, you might consider this simple scheme . . . Hobby Circuit designed by David A. Johnson P.E.-August, 2009

Cell Phone Solar Powered Charger -  The simple circuit below regulates the voltage from a 6v solar panel to a fixed +5v.  That voltage can be fed to any cell phone or USB connected portable device, to charge its battery.  The circuit uses a Reg113-5 voltage regulator from Texas Instruments . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2011

Cut Phone Line Alarm -  Burglars, rapists and other criminals will often cut a phone line before they break into a home.  The cut phone line will prevent many alarm systems from alerting the police.  The battery powered circuit below will sound an alarm when the unit. . . Circuit by Dave Johnson P.E.-October, 2005

Display RF Signal Strength -  Many cordless telephones, computer networks and cell phones use a RF transmitter lefted on the 2.45GHz band.  Using a microwave diode detector and 100uA meter, this passive circuit will display the strength this signal.  The drawing shows how a bent piece of wire can be used as the antenna. . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

DIY Cell Phone Charger -  It seems that as cell phones become more sophisticated, their operating times become shorter and shorter.  If you are on the go all the time and have difficulty finding AC or DC outlets to charge your phone, you might consider this simple scheme . . . Hobby Circuit designed by David Johnson P.E.-August, 2009

Do It Yourself Portable Cell Phone Charger -  It seems that as cell phones become more sophisticated, their operating times become shorter and shorter.  If you are on the go all the time and have difficulty finding AC or DC outlets to charge your phone, you might consider this simple scheme. . . Circuit by Dave Johnson P.E.-August, 2009

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

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Caller ID Display Service -  Caller iD decoder based on 68HC11, text in French __ Designed by Matthieu Benoit

Caller IDs -  information and circuits for different systems used USA and Finland __ Designed by Tomi Engdahl

Calling Bell using an Intercom -  Here is a simple calling bell circuit that can be used in small offices to call the office boy using an existing intercom system.  The office boy can be called from...__ Electronics Projects for You

Cell Phone Charger -  it seems that as cell phones become more sophisticated, their operating times become shorter and shorter.  if you are on the go all the time and have difficulty finding AC or DC outlets to charge your phone, you might consider this simple scheme . . . Hobby Circuit designed by David A. Johnson P.E.-August, 2009

Cell Phone Solar Powered Charger -  The simple circuit below regulates the voltage from a 6v solar panel to a fixed +5v.  That voltage can be fed to any cell phone or USB connected portable device, to charge its battery.  The circuit uses a Reg113-5 voltage regulator from Texas instruments . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2011

Cell-Phone calling Actuator -  Drives a relay when an incoming call is detected; 12V dc supply __ Contact Flavio Dellepiane, fladello @ tin.it

Cellphone Operated Land Rover. Part 1. Schematic -  Conventionally, wireless-controlled robots use RF circuits, which have the drawbacks of limited working range, limited frequency range and limited control.  Use of a mobile phone for robotic control can overcome these limitations.  it __ Designed by lik Zohaib

Cellphone Operated Land Rover. Part 2. Software -  Part 1.  Schematic Software description: The software is written in ‘C’ language and compiled using CodeVision AVR ‘C’ compiler.  The source program is converted into hex code by the compiler.  Burn this hex code __ Designed by lik Zohaib

Cellphone-Based Device Control with Voice Acknowledgement -  Here is a circuit that lets you operate your home appliances like lights and water pump from your office or any other remote place.  So if you forgot to switch off...__ Electronics Projects for You

Cellphone-Based Remote Controller for Water Pump -  inconvenience in switching on a water pump installed in a remote farm is a common problem faced by farmers.  Many circuits have been developed to solve this problem.  Most of them...__ Electronics Projects for You

Cell-Phone-Controlled Audio/ Video Mute Switch -  This cell-phone-controlled audio/video mute switch is highly useful in automobiles.  The circuit automatically disconnects power supply to the audio/video system whenever the mobile handset is lifted off the holder for making...__ Electronics Projects for You

Cellular Phone calling Detector -  This circuit was designed to detect when a call is incoming in a cellular phone (even when the calling tone of the device is switched-off) by means of a flashing LED.
The device must be placed a few centimeters from the cellular phone, so its sensor coil L1 can detect the field emitted by the phone receiver during an incoming call. __ Designed by Michael LaLena

Cellular Phone calling Detector -  Flashes a LED when detecting an incoming call; Powered by one 1.5V cell __ Contact Flavio Dellepiane, fladello @ tin.it

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, __ Linear Technology/Analog Devices

Chip recorder customizes phone ringer -  07/25/02 EDN Design Ideas:  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 Design by Don Schelle and Ted Salazar, Maxim Integrated Products, Sunnyvale, CA

Circuit provides message on disabled phone line -  01/20/00 EDN Design Ideas:  Phone companies often disconnect a misbehaving phone line from a complainant's residence for troubleshooting purposes.  With the problem between the residence and the central office, the residence is left with a dead phone line an __ Circuit Design by Kevin Kelly

Circuit translates a law to m law -  05/07/98 EDN Design Ideas:  (NOTE: contains several ideas, scroll down) Two common methods exist to compand voice for transmission through a PCM channel.  in Europe, A law involves converting a 12-bit input signal to an 8-bit encoded output.  in the US, m law involves encoding 13 bits to 8 bits.  You can use a translator to convert from A law to m law (Figure 1).  The converter is asynchronous and requires only an 8-bit A law input to provide an 8-bit m law output. __ Circuit Design by Rolando Herrero, Instituto Tecnológico de Buenos Aires, Argentina

Circuit Vocalizes Telephone Number -  02/03/94 EDN Design Ideas:  The circuit in Fig 1 is a simple method of vocalizing the digit number of a telephone keypad, which, for someone visually impaired, provide as 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 __ Circuit Design by Shwang-Shi Bai,  Chun-Shan Institute of Science and Technology, Lung-Tan, Taiwan

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, __ Linear Technology/Analog Devices

Clip Extracts Signal from Phone Line -  07/24/03  EDN Design Ideas:  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 leav __ Circuit Design by Maxwell Strange, Fulton, MD

Collection of Telephone Circuits -  Several design, scroll to find the one which interests you - telephone in-use indicator; telephone ringer; surfer's preserver __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Compact DJ Station -  Two Phono/Line switchable inputs; Powered by 9V Battery or external supply Adaptor __ Contact Flavio Dellepiane, fladello @ tin.it

Connect a Modem to a Basic Stamp -  09/16/99 EDN Design Ideas:  The 2400-bps modem in Figure 1 makes it easy to connect a Basic Stamp (Parallax inc, www.parallaxinc.com) to a telephone modem.  Using this circuit, you can call home via your PC and find out if the house is still there.  The Basic Stamp2, BS2-IC , has the necessary programming space, and a 64-kbyte StampMEM memory-storage board enhances site data collection.    __ Circuit Design by Ken Gracey

Contactless Telephone Ringer -  This fully transistorised, simple circuit designed as a contactless telephone ringer provides an indication of incoming telephone call at a remote site like kitchen or bedroom in the building.  it is...__ Electronics Projects for You

Conversation Recorder -  This circuit enables automatic switching-on of the tape recorder when the handset is lifted.  The tape recorder gets switched off when the handset is replaced.  The signals are suitably attenuated to a level at which they can be recorded using the ?MIC -iN? socket of the tape recorder__ 

Convert your smartphone into a pedometer & tracking Device -  EDN Design Ideas:  10/22/12    When you go hiking or mountain biking, or simply take a long walk around the neighborhood, you might wonder about the distance you covered or specific details, such as speed.  A specialized device for such a task is an expensive idea.  Now, however, the increasing penetration of smartphones in the market with built-in GPS devices makes it possible to configure a mobile phone to log or send the current readings from its sensors to a server for viewing and processing.   This design idea describes a simple approach to log readings from a GPS using the Python scripting language.  An advantage of Python is that an electronics engineer need not delve into the complex realm of C/C++ calls for Symbian/Android architectures to accomplish this simple task.  All that is required is the installation on a phone of the Python interpreter, along with a text file containing the script.    __ Circuit Design by Ali Asgher Mansoor Habiby and Abdus Sami Abdul Qayyum, Sir Syed University, Karachi, Pakistan

Cordless Phone Backup -  Normally the base of a cordless phone has an adaptor and the handset has Ni-Cd cells for its operation.  The base unit becomes inoperative in case of power failure.  Under such...__ Electronics Projects for You

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__ 

Cut Phone Line Alarm -  Burglars, rapists and other criminals will often cut a phone line before they break into a home.  The cut phone line will prevent many alarm systems from alerting the police.  The battery powered circuit below will sound an alarm when the unit. . . Circuit by Dave Johnson P.E.-October, 2005

Cut Phone Line Detector -  A while ago I got an email asking for the schematic of a circuit to detect cut phone lines.  it didn't take me long to find this circuit in Electronics Now.  When the circuit detects that a phone line has been cut, it activates a MOSFET which can be used to drive a relay, motor, etc.  it can also be connected to a security system __ Designed by Aaron Cake

Cut Phone Line Detector -  This circuit speaks for itself.    When the phone line is okay, Q1 acts as a short with a very high ohms value via R1, R2, and R3 for a total of about 66 MegOhm so very high.  When the phone line is cut (Tony van Roon's open) , it activates the MOSFET (Tony van Roon's Q3) via transistor Q2 to drive the load.    Substitutes are fine, none of the components are critical __ Designed by Tony van Roon  VA3AVR

DAA emulates central-office operation -  07/08/98 EDN Design Ideas:  A modification of a DAA's interface provide as central-office-like operation for single-line telephones. __ Circuit Design by Jerzy Chrzaszcz, Warsaw University of Technology, Poland

Designing High-Speed Digital Systems for Logic Analyzer Probing -  Application Note__ Aligent

Detect when phone line in use & when two telephones are on the same line -  This project has two features.  it will let you know when a single phone is using the line and also when two phones are on the line!  The green LED indicates the first phone and the red LED indicates the second phone!  __ Contact Collin Mitchell

Detecting a telephone RING 1 -  Mostly, there is only DC or small signal AC (audio) on the phone line.  C1 blocks the DC, and the R3-R2 voltage divider prevents the low level AC from having any effect.  When the ring signal comes along (90V RMS) enough voltage is developed at the juncture of R3 and R2 that (__ 

Detecting a telephone RING 2 -  My computer is in the basement and this device tells me if the phone line is in use.  I have inserted a N/O switch in the battery connection so that the batteries will last longer as sometime my sons spend a lot of time on the phone.  Prior to using my modem I press the switch to find out if the line is busy.  __ 

Detecting a telephone RING 3 -  This circuit requires a separate 5 volt supply.  The branch of the circuit that contains C1, C2 & R5, R6 is only used as a passive tap. (So you can record the line when the rest of the circuit says 'off hook'.  it can be removed if not needed.  if used, it can directly drive a microphone input to a portable recoreder.  __ 

Detecting a telephone RING 4 -  The transistor is a PNP Motorola 3638 with hFE of around 100 (probably doesn't matter).  Also, you could use this with different supply voltages if you change the 220k resistor.  Also, in case anybody's interested, I found the on-hook open-circuit voltage of my phone line to be 48.7V, and the short circuit current to be 72.8mA.  This leads to the conclusion that the line has a resistance of about 670 ohms.  There have been a few calls recently in sci.  electronics for phone in use circuits (ie a circuit that lights a LED when an extension phone is off hook).  __ 

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.  __ 

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Telephone Circuits:   #'s - B       C - F       G - K       L - Q       R - S      T - Z

 


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