Electronic Circuits and electronic circuits, electronic schematics plus an extensive resource for hobbyists, inventors and engineers

DiscoverCircuits.com, has 45,000+ electronic circuits, cross-referenced
into 500+ categories.    We have searched the web to help you find quick design ideas.
We make every effort to link to original material posted by the designer. 
Please let us if you would like us to link to or post your design.

HOME Schematics Index Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches

Got Designs?
Please eMail
if you want me to link to and/or post your original design Thanks.

Telephone Circuits

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

Last Updated: January 01, 2018 04:02 AM

Circuits Designed by Dave Johnson, P.E. :
Telephone Status Indicator for 4 Lines -  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 . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

Two 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.  The circuit is line polarity insensitive . . . Hobby Circuit designed by David Johnson P.E.-June, 2000

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-368-7747

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Talking Phone Dial Monitor -  Speaks the numbers that you dial as you dial your telephone.5 pages.  Not available as a kit of parts.  __ Golab.com

Taxi Phone Automatic Dialler -  This project is a dedicated device.  it dials a single phone number when the handset is lifted.  There are two different modes of operation..  A slide-switch on the PC board allows the project to operate in automatic or manual mode.  if the switch is in "auto dial" mode, a pre-programmed phone number is  AUTOMATIC ALLY dialled when the phone is lifted.  if the switch is in "push to dial, "  the project dials the number when the phone is lifted and "push to dial" button is pressed.  This allows the phone to be used as a normal phone.   __ Designed by Colin Mittchel

TDR Reflectometer -  Simple circuit to connect telephone equipment to audio mixer __ Designed by Tomi Engdahl

Tele Conferencing System -  Here is a low-cost tele conferencing system that lets you talk to two persons at a time in any part of the world over two telephone lines.  The circuit makes use...__ Electronics Projects for You

Tele-Call Interceptor -  PIC  Project  This device connects between the phone line, an answering machine, and your phones.  When a phone call comes in, the answering machine picks up the call and informs the caller to enter the access code to ring the phone or to wait for the beep and leave a message.  if the correct code is entered, the answering machine is immediately disconnected while the device generates phone ringing tones on an external speaker.  Picking up any phone causes the device to return to its initial state.   __ Designed by Luhan Monat-Mesa Arizona

Telecard reader -  This telecard reader can read the contain of any  telecard until 64 bytes (512 bits) and display it  to  hyper terminal software, using RS232 port __ Designed by © Vassilis Serasidis

Telephone #Display -  The given circuit, when connected in parallel to a telephone, displays the number dialed from the telephone set using the DTMF mode.  This circuit can also show the number dialed from the phone of the called party.  This is particularly heLPFul for receiving any number over the phone lines.  The DTMF signal—generated by the phone on__ 

Telephone (Bug) Transmitter FM  -  Receive telephone conversations on any FM radio with this neat little device.   __ Designed by Tony van Roon  VA3AVR

Telephone Amplifier -  While talking to a distant sub- scriber on telephone, quite often we feel frustrated when the voice of the distant subscriber is so faint that it is barely intelligible.  To overcome the problem, circuit of an inexpensive amplifier is presented here.  it can be assembled and tested easily.  There is no extra power source needed to power up the circuit, as it draws power from the telephone line itself.  The amplifier will provide fairly good volume for the telephone conversation to be properly heard in a living room.  A volume control is included to adjust the volume as desired.  The circuit is built around IC LM386.   __ Contact IQ Technologies

Telephone Audio Interface -  Audio from a telephone line can be obtained using a transformer and capacitor to isolate the line from external equipment.  A non-polarized capacitor is placed in series with the transformer line connection to prevent DC current from flowing in the transformer winding which may prevent the line from returning to the on-hook state.  The capacitor should have a voltage rating above the peak ring voltage of 90 volts plus the on-hook voltage of 48 volts __ Designed by Bill Bowden

Telephone Autodialler -  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.  So, read on and see what we have included __ Designed by Prepared Colin Mitchell

Telephone Call Logger -  it logs all outgoing calls and can download the data via your PC's serial port to an Excel spreadsheet.__ SiliconChip

Telephone Call Meter using Calculator & Cob -  in this circuit, a simple calculator, in conjunction with a COB (chip-onboard) from an analogue quartz clock, is used to make a telephone call meter.  The calculator enables conversion of STD/...__ Electronics Projects for You

Telephone Call Recorder -  Today telephone has become an integral part of our lives.  it is the most widely used communication device in the world.  Owing to its immense popularity and widespread use, there arises...__ Electronics Projects for You

Telephone call screener with voice -  PIC  Project  This unit is an upgrade of the previous phone call interceptor.  instead of using an answering machine to provide the outgoing message and recording functions, it uses the iSD4004 (from Windbond Electronics).  The iSD4004 records up to 8 minutes of audio.  I use the first several seconds for outgoing message prompts.  The remaining time is used to record up to 30 messages, depending on message length.   __ Designed by Luhan Monat-Mesa Arizona

Telephone call Voice Changer -  Voice manipulation device specially intended for props 9V Battery operation __ Contact Flavio Dellepiane, fladello @ tin.it

Telephone Controlled Night Light -  When the telephone rings, or when the handset is lifted, the night light is turned on and remains on while the conversation takes place.  When the handset is replaced in the cradle, the light remains on for about 11 s.  During standby conditions, the -28Vdc bias on the phone line maintains the__ 

Telephone 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...__ Electronics Projects for You

Telephone Dial Tone Generator -  This circuit provides a 1 volt peak-to-peak dial tone signal with equal proportions of 350Hz and 440Hz sine waves.  The two frequencies are generated in multivibrator sections U1A and U1B.  Triangle-like waveforms from the multivibrator sections are fed to summing amplifier U1D.  A 470pF capacitor in the feedback path of U1D removes some of the unwanted harmonics from the composite waveform, which is then fed to section U1C, a Sallen-Key low-pass filter.  U1C further reduces the harmonics, providing a high-quality summed-sine signal at its output.  The two frequencies are close enough to permit a single-filter design, with the summing resistors at U1D's input selected to emphasize the 440Hz component, accordingly __ Designed by Arthur Harrison

Telephone Headgear -  A compact, inexpensive and low component count telecom headset can be constructed using two readily available transistors and a few other electronic components.  Since the circuit draws very little current, it is ideal for parallel operation with electronic Telephone set__ 

Telephone Headset Adaptor -  Keep your hands free with this simple low-cost project.  it can be used with any phone that uses RJ11 modular plugs and sockets.__ SiliconChip

Telephone Headset Amplifier -  This circuit goes between a telephone and a headset.  The project has a headset cord and plug (cut from a cheap cell phone headset) on the input and a suitable jack on the output.  The speaker signal passes through this circuit, but the microphone signal is  __ Designed by Andrew R. Morris

Telephone Hold Button -  Although a hold feature is standard on most new phones, a lot of us still use the origional bell phones.  Those of us that require a hold feature will find this circuit very useful.  it is easy to build, and is compact enough to be installed inside the phone with no real problem.  it is also powered by the phone line itself, eliminating the need for batteries __ Designed by Aaron Cake

Telephone In Use Indicator -  This circuit will illuminate a LED if one of your telephones is in use.  it should work in all countries (including UK) that have a standing line voltage above 48 Volts DC.   __ Designed by Miroslav Adzic

Telephone in Use Relay -  Circuit to close a relay when any telephone extension is off the hook.   __ Designed by Bill Bowden

Telephone In-Use Indicator -  Several design, scroll to find the one.   When a new computer modem enters the household, the demands on the home phone line skyrockets.  The internet surfer can use phone time on a par with the most talkative teenager.  And the computer modem user can be quite sensitive about his privacy: simply lifting another receiver can knock him off-line causing emotional stress.  The phone wiring may be modified so that the modem is always in control by connecting the phone line directly to the modem and connecting the rest of the phones to the modem's "phone" jack. __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Telephone In-Use LED Indicator -  Circuit to illuminate an LED when any telephone extension is off the hook.   __ Designed by Bill Bowden

Telephone Lamp -  Here is a White LED Lamp that turns on when the telephone rings.  The cool white light helps to locate the phone in darkness and also helps to note the message or telephone number.  The lamp remains on for three minutes then turns off.  The telephone lamp circuit is powered by a 9 volt PP3 battery and connected to the telephone __ Designed by D Mohankumar

Telephone Line Audio Interface -  This device connects the telephone line to a home theater system or PA system (receiver only).  it is phone line powered and features automatic volume control (AVC).  it also mutest itself when a phone is picked up to prevent feedback.   __ Designed by Andrew R. Morris

Telephone Line Audio Interfaces -  Telephone recording, Telephone line to mixer and Telephone hybrid circuits __ Designed by Tomi Engdahl

Telephone line based audio muting & light on -  Very often when enjoying music or watching TV at high audio level, we may not be able to hear a telephone ring and thus miss an important incoming phone call.  To overcome this situation, the circuit presented here can be used.  The circuit would automatically light a bulb on arrival of a telephone ring and simultaneously mute the music system/TV audio__ 

Telephone Line Based Audio Muting & Light-On Circuit -  Very often when enjoying music or watching TV at high audio level, we may not be able to hear a telephone ring and thus miss an important incoming phone call.  To...__ Electronics Projects for You

Telephone Line Filter / Protector -  To build a circuit that will help protect your equipment from lightning strikes on the phone line.  This circuit was actually designed to reduce or eliminate a very local broadcast AM radio stations signal from bombarding my parents telephone line, however it also turned out to be a really good lightning protector.  __ Designed by Kevin Custer  W3KKC

Telephone Line In-Use Indicator -  This circuit gives a visual indication of whether a telephone line is in use or not, helping two or more people sharing the line to avoid interrupting each other's calls.  As...__ Electronics Projects for You

Telephone line Monitor -  if you feel that somebody is tampering with your telephone line you might find this little circuit useful.  it detects if there is another telephone connected to the line, if there is a short or an open line.  Sound and a flashing light will tell you which is the current situation.  The speaker is practically cut out during a normal conversation thus preserving privacy, only the LED will flash occasionally.  The circuit does not require any battery and takes the supply from the telephone line itself __ Contact IQ Technologies

Telephone Line Monitor (Plans) -  When the Dispatcher picks up the phone (in a standard circuit, I have NO clue what your PBX does.  this will work on standard home phones, and I used to use it for a tape-recording controller) Hey, there's an idea, spend $25 on a telephone recording device, and hitch it to a nice loud amp and speaker combo, instead of a tape deck.  it'll save you loads of time__ 

Telephone line simulator -  The following text describes construction, testing and use of an electronic telephone line simulator of my own design.  This self-build project can simulate a telephone call / connection between any two local telephone devices.  This for a fraction of the outlay of some commercial units, many with cost-increasing features that usually are not required.   __ Designed by S Chalmers

Telephone line simulator ideal for testing phone interface projects -  Creating projects that connect to the phone line can be a real chore without some device like this.  it generates the 48 volts DC for the on-hook condition, the 100 volts AC for the ring signal, and the 20 milliamperes DC for the off-hook condition __ Designed by Luhan Monat-Mesa Arizona

Telephone Line Vigilant -  Here is a telephone line vigilant circuit to guard against misuse of your telephone lines.  it monitors telephone lines round the clock and provides visual as well as an audio warning (when someone is using your telephone lines) which can be heard anywhere in the house.  Another advantage of using this circuit is that__ 

Telephone Listening Bug -  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.  __ 

Telephone Off-Hook Indicator -  This circuit provides a steady logical "high" indication when the telephone is off its hook.  Operation is as follows:During the off-hook condition, DC telephone line voltage flows through clamping diodes CR1 and CR2, which develop about 1.5 volts across resistor R1.  This voltage is provided to the input of optical coupler U1 via current-limiting resistor R2, turning on U1's internal light-emitting diode.  Under these conditions, U1's NPN output transistor turns on, providing the +5 to +15 volt logic "high" level at its emitter, pin 4.  Pin 4 of the coupler may be connected to subsequent indicator circuitry, such as a transistor-controlled lamp or audible device.   __ Designed by Arthur Harrison

Telephone Off-Hook Tone Generator -  This circuit generates the sound that many telephone companies use to attract the customer's attention to their phone when they leave it "off hook.  " it is also refered to, in telephony jargon, as "ROH, " for "receiver off-hook.  " The sound is comprised of four sine waveforms, added in equal proportions, and keyed on and off at a rate of 5 Hertz.  in practice, the sequence is usually administered in two 50-second servings, preceded by a recorded announcement requesting that the phone be put back on its hook.   __ Designed by Arthur Harrison

Got Designs?
Please eMail
if you want me to link to and/or post your original design Thanks.


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

HOME Schematics Index Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches

 About Us   |  Advertise on DiscoverCircuits.com   |   Report Broken Links  |    Link to DiscoverCircuits.com  |    Privacy Policy

Copyright  January, 1998 - January, 2018     David A. Johnson & Associates.  All Rights reserved. 

 Linking is ALLOWED but COPYING any content or graphics to your web site is EXPRESSLY PROHIBITED.