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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. :

RF 2.45Ghz Signal Detector -  This passive RF indicator is made from a few simple parts.  A 100uA moving coil meter is used to display the relative intensity of the RF signal.  This circuit can be used with some cell phones and many cordless telephones . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

RF Signal Detector at 2.45GHz -  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 Dave Johnson P.E.-July, 2006

Solar Powered Cell Phone 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. . . Circuit by David A. Johnson P.E.-January, 2011

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Radio Control made from Junk -  Here we are going to make a simple radio controlled device using supplies from your local dumpster.  This project should cost less than a dollar to make.  if you spend more than a dollar on this project, you need to dig more.   __ Designed by sixmhz @ yahoo.com

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__ 

Remote Phone-Bell Ringer -  Did you ever miss an important telephone call simply because you were away where you couldn't hear the phone ringing? This should not happen again with this inexpensive remote telephone bell....__ Electronics Projects for You

Remote Telephone Bell Ringer -  This remote telephone bell ringer allows you to use a large (and loud) external bell in place or in addition to the built in (and rather wussy) ringer in most modern telephones.  This is ideal for large outdoor areas, noisy shops or those hard of hearing.  Most any large bell can be used as the circuit can be easily adjusted for various supply voltages. __ Designed by Aaron Cake

Reproduction line cord resistor -  How to make an authentic replacement line cord resistor for your American AC/DC radio __ Contact blehack @ yahoo dot com

RF 2.45Ghz Signal Detector -  This passive RF indicator is made from a few simple parts.  A 100uA moving coil meter is used to display the relative intensity of the RF signal.  This circuit can be used with some cell phones and many cordless telephones . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

RF Signal Detector at 2.45GHz -  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 Dave Johnson P.E.-July, 2006

Ringing Phone Light Flasher -  This is very useful in a situation were there is lots of noise and it is impossable to hear the phone, such as a workshop.  Here is such a device.  The ring detect part of this circuit came from [url]http://www.  hut.  fi/Misc/Electronics/circuits/telephone_ringer.  html[/url].  Notes: 1.  You may need to use a lower voltage zener for D1 and D2.2.  You can use a regular relay instead of a solid state relay, but the arcing accross the contacts may destroy it pretty quickly.3.  Be very sure that you have not accidentally connected 120V to the phone line when building and installing this __ Designed by Aaron Cake

Ringing Phone Light Flasher -  I have received several emails asking how to connect up some lights so that when the phone rings, they flash. This is very useful in a situation were there is lots of noise and it is impossable to hear the phone, such as a workshop. Here is such a device __ Contact IQ Technologies

Ringing Phone Light Flasher using optocoupler & relay -  I have received several emails asking how to connect up some lights so that when the phone rings, they flash. This is very useful in a situation were there is lots of noise and it is impossable to hear the phone, such as a workshop. Here is such a device. __ Designed by Aaron Cake

Self-powered phone messenger -  I always keep one totally self powered phone (the way they all used to work) in case of a power failure.  This device works the same way, taking all of its power directly from the phone line. __ Designed by Luhan Monat-Mesa Arizona

Silicon MW Broadband Amplifier MMIC's 7/20/88  -  App Note  Doc #918__ California Eastern Laboratories

Simple 7 band eqalizer -  Audio graphic equalizers are very common as commercial products (for Hi-fi, car audio and stage use) but circuits for them are very rarely published.  I didn't design this one but it's really very simple.  The details shown are for a 7 band but the principle can be extended to almost any number of bands - if you can find accurate enough components. __ Designed by Richard Torrens

Simple Circuit Alarm with telephone dialler interface -  This is the lowest cost dialing alarm on the market and shows what can be done with an 8-pin microcontroller.  The complete circuit is shown below.  You cannot see all the features of this project by looking at the circuit - most of them are contained in the program __ Designed by Colin Mitchell, Talking Electronics

Simple Circuit intercom -  Perhaps you need an intercom. Maybe you want to be able to communicate with your house from your shed or garage. Or perhaps as in my case some years ago, you are upstairs in your bedroom doing your schoolwork, you want to know when dinner will be ready, and you are too lazy to get up and shout down the stairs to find out. if so, then this simple intercom project is for you. I have made many of these and never had any trouble getting them working.  __ Designed by Hans Summers

Simple Circuit Phone Tap -  Will record any conversation on any ph1-on same line, the circuit seems to be a bad design because it does not provide proper isolation and has too low DC impedance (can keep you line off-hook all the Time)  __ Designed by Aaron Cake

Simple Circuit Phone Tap -  This circuit is extremely simple, therefore there is less chance of any problems. it can be placed anywhere on the phone line and it will record any conversation on any phone on that line __ Designed by Derek Tombrello

Simple Circuit Radio Control from Junk -  Here we are going to make a simple radio controlled device using supplies from your local dumpster.  This project should cost less than a dollar to make.  if you spend more than a dollar on this project, you need to dig more.   __ Designed by sixmhz @ yahoo.com

Simple Circuit Skype VoIP analog adapter -  it’s a very cheap Skype/VoiP interface to your wired or wireless phone. __ Contact C. Järnåker

Simple Circuit speakerphone -  Small Loudspeaker is a fun project to do, you can connect it to your Cellphone or Laptop through a 3.5mm audio jack and can enjoy your own loudspeaker. You can also connect it to any device which has a 3.5 mm audio output, like TV, music player, video games etc. We have used LM386 IC to amplify sound, with a few external components.__ 

Simple Circuit Telephone Test -  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 __ Designed by Tomi Engdahl

Simple Circuit Valve Amplifiers -  A collection of economical low power amplifier designs using common low cost valves.   __ Contact blehack @ yahoo dot com

Simplery 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

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

Single Cell Flashes White LED -  12/11/03 EDN Design Ideas:  Many portable appliances and other products that must operate from a single cell are restricted to working at very low voltages.  it is thus difficult to drive white LEDs that typically have a forward voltage of 3 to 5V.  The ability __ Circuit Design by Anthony Smith, Scitech, Biddenham, Bedfordshire, UK

Single-Wire-Telephones for caves & mines -  The Single-Wire-Telephone (SWT) has replaced the Army "field telephones" as the weapon of choice for wired cave and mine rescue communications.  The devices are very simple, using a single op-amp to both send and receive an audio signal (voice) along a single insulated wire, using the operators coupling capacitance to ground for the return.  The receiver has a very high input impedance.  Power demand is very low, with many hours (or days) of operation from a 9 Volt battery.__ 

Small Capacitor Supports Telecom Power Supply During Brownouts -  05/15/08  EDN Design Ideas:  By using a charge pump, the energy stored in a small capacitor can support the operation of a "brick" telecom power supply during brownouts __ Circuit Design by Samuel Kerem, Rockville, MD

Smart Phone Light -  The circuit shown here is used to switch on a lamp when the telephone rings, provided that the ambient light is insufficient. The circuit can be implemented using just two IC S.  A...__ Electronics Projects for You

Smart Phone light -  The circuit shown here is used to switch on a lamp when the Telephone rings, if the ambient light is insufficient.  __ 

Smart Ringing Phone Light -  The circuit shown here is used to switch on a lamp when the Telephone rings, if the ambient light is insufficient.  __ 

Soft Musical Telephone Ringer -  The normal telephone bell, at times (specially during night when one does not want to be disturbed) , appears to be quite irritating.     The circuit shown here converts the loud sounding bell into a soft and pleasing musical tone. __ Contact IQ Technologies

Soft On/Off Switch -  Modern electronic equipment incorporate "push-to-on-push-to-off" switches that do not make noise as with old equipment.  An example of this is the power button on a ATX computer cabinet.  Here is a circuit that does the same.  it can be used to turn on/off__ 

Solar Powered Cell Phone 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. . . Circuit by David A. Johnson P.E.-January, 2011

Supervisory Monitors-modem connection -  04/09/98 EDN Design Ideas:  (Scroll to find this circuit) in telemetry or security applications in which a modem connection automatically establishes itself between two systems, a failure in one of the systems can interrupt the data exchange while the connection remains established until someone physically breaks the line or restarts the failed system.  This situation __ Circuit Design by J Basilio Simies and Jorge Landeck, Instrumentation Center of the University of Coimbra, Coimbra, Portugal

Switched-Capacitor IC & Reference Form Elegant –48 to +10V Converter -  04/24/03  EDN Design Ideas:  A system designer must almost always face a trade-off in choosing the right part for an application.  The trade-off usually involves performance, price, and function.  An example is the issue of powering circuits from a telecom-voltage source.  Telecom systems almost exclusively use high-potential negative rails, such as -48V __ Circuit Design by Wallace Ly, National Semiconductor, Santa Clara, CA

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

 


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