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Talking Phone Dial Monitor - (electronic schematic / circuit added 4/02) |
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Taxi Phone Automatic Dialler - (circuit / design added 8/03) |
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TCP/IP Library Programmer's Guide - Silicon Labs Application Notes (app note
added 6/06) |
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TDR Reflectometer - (electronic schematic / circuit added 4/02) |
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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.….(design added 05/09) |
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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. ….(electronic schematic added
11/08) |
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Telephone Audio Interface - (circuit / design added 8/03) |
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Telephone Audio Interface circuitdb - 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.... (added
05/06/07) |
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Telephone Autodialler - (circuit / design added 8/03) |
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Telephone call meter using calculator & COB - In this circuit, a simple
calculator, in conjunction with a COB (chip-on-board) from an analogue quartz clock,
is used to make a telephone call meter. The calculator enables conversion of STD/ISD
calls to local call equivalents and always displays current local call-meter reading.
The circuit is simple and presents an elegant look, with feather-touch .... (added
1/065) |
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Telephone call Voice Changer - Voice manipulation device specially intended for
props 9V Battery operation (added 05/06/07) |
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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....(electronic Circuit / Schematic added 10/04) |
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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 a level at which they
can be recorded using the ‘MIC-IN’ socket of the tape recorder. ….(electronic
schematic added 11/08) |
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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. (added 10/05) |
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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 passed straight from the plug to the jack. This
circuit is specifically designed for ultra.....Designed by Andrew R. Morris (added
09/05) |
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Telephone Hold Button (Aaron Cake) - (electronic schematic / circuit added
04/03/02) |
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Telephone in Use LED Indicator - (circuit / design added 8/03) |
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Telephone in use Light - ASCII format (circuit / design added 8/03) |
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Telephone in Use monitor - (schematic / circuit added 6/07) |
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Telephone in Use Relay Circuit - (circuit / design added 8/03) |
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Telephone In-Use Indicator - Allows to record important telephone conversations.
….(electronic schematic added 11/08) |
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Telephone In-Use LED Indicator - (circuit / schematic added 6/05) |
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Telephone in-use light - (electronic design added 6/07) |
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Telephone In-Use Relay Circuit - (circuit / schematic added 6/05) |
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Telephone Line Audio Interface Circuits - Telephone recording, Telephone line to
mixer and Telephone hybrid circuits (added 2/03) |
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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 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 ....
(added 10/05) |
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Telephone Line Based Audio Muting & Light-On Circuit - (electronic Circuit /
Schematic added 10/04) |
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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 .... (added 9/07) |
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Telephone Line Monitor (ee.washington.edu) - ASCII format (circuit / design added
8/03) |
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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...(electronic design added
6/07) |
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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.... (added 10/05) |
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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.
….(design added 11/08) |
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Telephone Number Display - The given circuit, when connected in parallel to a
telephone, displays the number dialled from the telephone set using the DTMF mode.
This circuit can also show the number dialled 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 .... (added 10/05) |
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Telephone Number Display EFYLinux - (electronic Circuit / Schematic added 10/04) |
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Telephone operated remote control using PIC16F84A microController - This design
controls up to 8 devices using a PIC microcontroller (PIC16F84A) connected to the
phone line. The unique feature here is that unlike other telephone line based remote
control, this device does not need the call to be answered at the remote end so the
call will not be charged. This device depends on number of rings given on the
telephone line to activate/deactivate devices.... (added 10/05) |
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Telephone Power? - ASCII format (electronic Circuit diagram added 03/03/03) |
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Telephone Privacy Adapter - (electronic schematic / circuit added 4/02) |
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Telephone Receiver - An interesting circuit and handy electronic telephone
receiver, suited for receiving incoming calls, is described here. This circuit can be
connected to almost all types of telephone exchange lines. To simplify the gadget, the
dialer section has been omitted. The circuit can be constructed on a medium size
veroboard. ….(circuit design added 11/08) |
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Telephone Record Control (Randy Linscott) - This circuit will allow you to connect
any tape recorder that has a mic and remote input to a phone line and automatically
record both sides of a conversation when ever the phone is in use.You will need to
take a couple of voltage readings before connecting the circuit….(added 3/03) |
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Telephone Recorder (Aaron Cake) - This circuit lets you record your
ph1-conversations automatically, notice that this circuit does not provide isolation
between Telephone line and the recorder (added 5/02) |
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Telephone Recorder tjacodesign - This circuit automatically records all incoming
and outgoing phone-conversations with an ordinary cassette or tape recorder. The
circuit below distills the audio signal from the phone-line and automatically
starts/stops the cassette recorder. (added 5/02) |
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Telephone Recording Circuit epanorama - How they work and some example (added
5/02) |
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Telephone Recording Switch - Switches on a Tape Recorder and records both sides of
the conversation, when a phone is picked up. Useful to log all telephone
conversations. (circuit design added 7/06) |
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Telephone Remote Switch - This device connects to the telephone line and can be
used to remotely control up to 4 relay outputs using a DTMF (tone dialing) telephone.
A number of user settings are available to improve the useability and security of the
device. The kit comes complete with a small plastic case with silk-screened front and
rear panels. ….(electronic schematic added 11/08) |
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Telephone Ring Generator using 60hz Power Transformer - This ring generator will
ring a telephone once every 10 seconds. The interval between rings can be lengthened
or shortened by varying the value of the 1 Meg resistor. The 70 volt/ 30 Hz ring
voltage is produced from the 120 volt side of a small 12.6 VAC power transformer
....(circuit / design added 8/03) |
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Telephone Ring Generator using Switching Power Supply - The telephone ring
generator shown below generates the needed high voltage from a simple switching mode
power supply (SMPS) which employs a CMOS Schmitt Trigger square wave oscillator, 10 mH
inductor, high voltage switching transistor (TIP47 or other high voltage, 1 amp
transistor) and a driver transistor (2N3053). The inductor should have a low DC
resistance of 1.5 ohms or less. The switching supply must have a load connected to
prevent the voltage from rising too high, so a 22K resistor is .... (diagram added
8/03) |
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Telephone Ringer by IC KA2411 - Simple telephone Ringer with KA2411 IC. ….(design
added 11/08) |
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Telephone Ringer using 555 Dual Timers - Using modulated rectangular waves of
different time periods, The circuit presented here produces ringing tones similar to
those produced by a telephone. The circuit requires four astable multivibrators for
its working. Therefore two 556 ICs are used here. The IC 556 contains two timers
(similar to 555 ICs) in a single package. One can also assemble.... (added 10/05) |
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Telephone Ringer using Timer ICs - (electronic Circuit / Schematic added 10/04) |
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Telephone Ringing Circuits - how to detect ringing and how to make phones ring
(added 5/02) |
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Telephone Ring-Tone Generation - DN134 Design Notes (Linear Technology) (app note
added 2/06) |
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Telephone Tap - Amplify or record a telephone call with the simple circuit shown.
The 8-W secondary winding of a miniature transistor output transformer is connected in
series with either of the telephone lines. The 1000-W primary winding can feed either
a cassette recorder or an audio amplifier....(electronic design added 6/07) |
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Telephone Test Circuit with Audio Mixer - get Telephone audio to mixer or send
audio to Telephone (added 4/05) |
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Telephone Transmitter FM - Receive telephone conversations on any FM radio with
this neat little device. (Tony van Roon's schematic added 2/06) |
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Telephone Voice Changer - Although this kind of voice effect can be obtained by
means of some audio computer programs, a few correspondents required a stand-alone
device, featuring microphone input and line or loudspeaker outputs. This design
fulfills these requirements by means of a variable gain microphone preamplifier built
around IC1A, a variable steep Wien-bridge pass-band filter centered at about 1KHz
provided by IC1B and an audio amplifier chip (IC2) driving the loudspeaker.
….(electronic schematic added 11/08) |
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TeleRemote Control - (electronic Circuit / Schematic added 10/04) |
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Teletext Devices - (circuit / schematic design added 6/06) |
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The KD2BD Pacsat Modem - (circuit / schematic added 6/05) |
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The Link "P"-Privacy Link! (Telephone Intercom) - ….(electronic schematic added
08/08) |
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The Link 4+0 – Internal Intercom - ….(circuit design added 08/08) |
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The Link A2B+1 (the Link Telephone Intercom-DTMF version) - ….(electronic
schematic added 08/08) |
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The Link Telephone Intercom – Every Home Should Have One! - The Link circuitry is
simple and efficient, employing just two ICs, half a dozen transistors, and a handful
of garden variety components. It all runs on 12 volts and is easily assembled. You can
have your own home intercom between the kitchen, the garage, the rumpus room and at
your poolside ‘barby’ and all for less than $100! The “Link” intercom.... (added
10/05) |
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The Original 2 Phone Link Design - ….(circuit design added 08/08) |
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Tiny Efficient High Power LED Camera Flash Solutions for Cell Phone Applications -
Linear Technology Design Note 1009 (app note added 02/05) |
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Two Line Intercom Cum Telephone Line Changeover Circuit - (electronic Circuit /
Schematic added 10/04) |
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Two Line Intercom Plus a Telephone Changeover Switch - The circuit presented here
can be used for connecting two telephones in parallel and also as a 2-line intercom.
Usually a single telephone is connected to a telephone line. If another telephone is
required at some distance, a parallel line is taken for connecting the other
telephone. In this simple parallel line operation, the main problem is loss.....
(added 5/02) |
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Two way Simple Very Small Telephone Exchange - ….(circuit design added 08/08) |
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Universal Telephone Hold - (electronic schematic / circuit added 4/02) |
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Unplugged Power Cord Alarm - Many medical devices, such a portable X-ray and
ultrasound equipment, carry their own batteries. However, the frantic pace of some
hospital emergency rooms might cause the device to be shoved off into a corner without
being plugged back into an AC power source to recharge their batteries. So, I designed
this circuit to emit an audible alarm whenever the device’s power cord was unplugged
from the wall for a period of time. The device was designed to snap onto the outside
of a power cord, where it senses the AC electric field emitted. No direct connection
to the internal wires of the power cord is needed. I also included a low battery
voltage monitor. ….(designed by David A. Johnson) |
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Use Amplifier phono input as Line Level input - The circuit does two functions:
signal level attenuation and inverse RIAA filtering. The signal attenuation is needed
to convert the 500 mV signal to 2.5 mV signal. The inverse-RIAA filtering is needed to
make the frequency response of the system flat (same equalization that is used when
music is transferred to vinyl in the studio)..... (added 4/05) |
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Use old Phones as an Intercom - ASCII format Now here's some logic that should
work fine with the right zener and the right resistors and a couple of cheap npn's
2n2222A's or 2n3904's (06's?). If you get close to 25 volts with the new smart test
boxes, a 20 volt Z may work fine. Choose R1 to limit current through Z and have enough
left to turn on npn1 just enough to deprive npn2, choose R2 for that, and you will
need to add a resistor R3 to protect the LED from overcurrent as needed, depending on
the phone system you have! (added 8/03) |
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Voice Record/ Playback Circuit - The ISD1000A is a Direct Analog Storage device
which allows you to store 20 seconds worth of voice data on an IC chip which can be
play backed anytime. The data stored will stay in memory even if the power is removed.
To use the circuit below simple apply power to the circuit, press the record button
and hold. Speak clearly into the microphone. You have up to 20 seconds….(added
08/08/08) |
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Voice Scrambler (Randy Linscott) - With this circuit you can modify how your voice
sounds by changing the pitch of your voice. This circuit can be connected to a phone
and with a duplicate circuit on the end of the phone line, you can have a scrambled
voice communication. The way the ….(added 05/02) |
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Voice Scrambler/Descrambler - This is a single-inversion voice
scrambler/descrambler. Though no longer useful for police scanners, it would be a fun
project for a hobbyist. It was designed for use on a 9-volt battery, but by changing
resistor values proportionately, it could be adapted to use whatever voltage is
available in your radio....Designed by Andrew R. Morris (added 09/05) |
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Watch-Dog for Telephones - Most of the telephone security devices available in
market are simple but quite expensive. These devices provide blinking or beeping type
line-tap/misuse indications. Quite often they do not offer guaranteed protection
against unauthor-ised operation. A very simple and uni- que circuit of a telephone
watch-dog to safeguard subscriber telephone lines against any fraud is described here.
This little circuit keeps continuous watch over the telephone lines and sounds an
alarm in case of any misuse. In addition it transmits a loud tone through the
telephone lines to prevent further misuse. ….(electronic schematic added 11/08) |
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Wireless Telephone Bug - Here's a neat little project that will allow you to
monitor your phone line as soon as your phone is off hook. You can use a regular FM
broadcast band radio to monitor the conversation. Just remember, it ….(circuit design
added 03/08) |
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Wireless Telephone Eavesdropper Electronic Circuit - The IR transmitter connects
to a telephone circuit, and transmits both sides of all telephone conversations to any
line-of-sight location, within 40 feet. No power is taken from the central office, as
long as all phones remain on-hook. The current flows through the phone and back to the
central office....(electronic design added 6/07) |
