Telephone circuits ( 96 ) :

• Telephone equipments

• ITT Telephone Instrument Maintenance Manual - Much of the information contained in this manual parallels similar equipment information for Western Electric, Stromberg Carlson, etc. since Western Electric licensed much of their technology and product specifications to companies like ITT who provided equipment to the "Independent" telephone companies.   
• Miniature Beige Box Design - Simple telephone with microphone and speaker quite similar to lineman's handset.   
• Telephone Headgear - This circuit is very useful for hands-free operation of EPABX and pager communication. This circuit can be used in parallel with existing electronic telephone set.   
• Telephone Schematics for Western Electric Phones - Schematics, Drawings and Tables from Station Service Manual to view/download     
• Telephone Tribute Technical Information - tutorials, technology information, repair information, telephone service manuals     
• Wiring Inside Phones - Since wiring inside most fones is pretty standard, this description should do the trick. This applies to all WE phones and ITT phones that use the standard dial/ringer/network block/handset configuration.     
   

• Audio Interfaces

• Building and using phone patches - article from Ham Radio Magazine October 1985   
• Build your own inductive telephone tap! - We're going to build an inductive telephone tap that will allow us to listen to telephone conversations nearly undetectably. This project uses only inexpensive and readily available parts.  
• Hands-Free Telephone - Tis is a circuit to interface telephone handset connector to stereo heaphone and small microphone. This circuits to connect to 4-pin telephone handset connector.     
• Headset-Adapter for Cisco-IP-Phone - You can connect a standard PC-Headset to the Cisco IP-Phone. The necessary adaptor is described here.     
• How do I hook the Sound Blaster output to play over the phone line - zipped file     
• Isolated Telephone Interface - This circuit allows you to record audio from a telephone line into a tape recorder or computer soundcard. Most of the parts for this circuit can be scrounged from an old modem, with some work, it is possible to rewire the modem circuitry and use the old modem case.     
• Playing a Mac through a standard telephone line - how to get sound from computer to telephone line     
• Phone Amplifier - This is a useful 0.5 watt amplifier for phone line, powered by a simple 10 volt supply. It uses an isolated trasformer to get the sound from the telephone line and an audio transformer for the amplifier output.     
• Phone "Hold" With Music     
• Phone "Hold" With Music - interface to a radio or CD player headphone jack     
• Phone Line to Audio     
• Phone to audio interface (SSI202 input)     
• Simple telephone test circuit - get telephone audio to mixer or send audio to telephone     
• Telephone Audio Interface - uses transformer and capacitor to isolate the line from external equipment, diode based surge protection on output     
• Telephone line audio interface circuits - telephone recording, telephone line to mixer and telephone hybrid circuits     
• Telephone Record Control - allows 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     
• Telephone recorder - 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 casette recorder.     
• Telephone Tap - wire your telephone conversion to amplifier or tape recorder
   

• Busy indicators and related circuits

• 1 line status indicator - circuit gives you a visual indication when a line is in operation, line polarity insensitive and operates from two AA batteries for one year, pdf file     
• 2 line telephone line status indicator - circuit gives you a visual indication when a line is in operation, line polarity insensitive and operates from two AA batteries for one year, pdf file     
• 4 line telephone line status indicator - circuit gives you a visual indication when a line is in operation, line polarity insensitive and operates from two AA batteries for one year, pdf file     
• Audio Visual Ringer - This is an extra telephone ringer circuit. All that needs to be done is to connect the given circuit in parallel with the existing telephone lines using twin flexible wires. This circuit does not require any external power source for its operation.     
• Free-line indicator stops interruptions - A simple circuit lights an LED, which indicates whether the line is free (Figure 1a). Batteries are unnecessary; the phone line powers the circuit, and an accumulator saves energy for an "in use" indication.     
• Phone-In-Use indicator - simple design idea for indicator     
• Phone in use circuits - two designs     
• Phone In Use Indicator     
• Telephone In-Use Indicator - versions for LED indicator and relay output     
• Telephone In-Use Indicator     
• Telephone In-Use Indicator, Telephone Ringer and The Surfers Preserver     
• Telephone privacy adapter - revents other telephones from hearing your call and disturbing your modem connection     
   

• Telephone recording and tape controlling

• Tape Recorder Switch for Telephone - This kit uses a FET to switch on a tape recorder when the phone is picked up. It will work with low voltage tape recorders as low as 1.5V. It requires the REMOTE & MIC jacks of the tape recorder to be available.     
• Telephone recording circuits - how they work and some example circuis     
   

• Ring detectors

• Audio Visual Ringer - extra ring detector with LED and sound output     
• Chip recorder customizes phone ringer - By placing a circuit in series with the telephone, you can customize a phone ringer without modifying the phone. The heart of the ringer is a chip-recorder IC, which can play as much as 10 seconds of telephone-quality recorded sound.     
• Phone rang indicator light - will detect the ring signal, energize the relay which latches up, and the LED comes on and stays on till you push a switch     
• Smart Phone light - The circuit shown here is used to switch on a lamp when the telephone rings, if the ambient light is insufficient.     
   

• Telephone line controlled muting and other related control

• Smart Phone light - The circuit shown here is used to switch on a lamp when the telephone rings, if the ambient light is insufficient.     
• Telephone line based audio muting and light on circuit     
• Telephone Line Based Audio Muting and Light-On Circuit - circuit would automatically light a bulb on arrival of a telephone ring and simultaneously mute the music system/TV audio for the duration the telephone handset is off-hook  
   

• Telephone hold circuits

• Music-On-Hold Box     
• Phone "Hold" With Music     
• Phone "Hold" With Music - interface to a radio or CD player headphone jack     
   

• Caller ID and DTMF decoding circuits

• Caller ID circuits and information - information and circuits for different systems used USA and Finland     
• Caller ID Display Service - caller ID decoder based on 68HC11, text in French     
• Caller ID / DTMF Audio Decoder Sources & Links     
• Caller ID / DTMF audio decoder     
• CID.ZIP - Adapter for getting aller ID information from Finnish telephone network to PC. THis circuit decodes DTMF format caller ID. This document includes source code (Pascal) for simple programs to access the circuit in DOS and Windows. The document language is Finnish.     
• DTMF Generator/Decoder - tutorial with example circuit diagrams     
• DTMF Products for you - DTMF decoder can be powered from a 9V battery or from your parallel printer, schematic and windows demo program, design by Schmidt Technologies     
• DTMF Tone Decoder with LCD Display - based on Basic Stamp microcontroller
• Generate CID/CIDCW analog signals - A high-speed �P can generate CID (caller-ID) and CIDCW (caller-ID-on-call- waiting) analog signals at 1200 baud FSK between the first and second 20-Hz ring of an incoming call     
• 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.     
   

• Dialler circuits

• Un composeur automatique de num�ro t�l�phonique - PC controlled DTMF dialler     
   

• Test equipments

• Digital/Standard Phone Line Tester - make sure that the line is suitable for modem use and your PCMCIA does not damage if you plug it in     
• Digital/Standard Phone Line Tester - telephone line polarity and current detector
• Off line Telephone tester - Here is a circuit of an off-line telephone tester which does not require any telephone line for testing a telephone instrument. The circuit is so simple that it can be easily assembled even by a novice having very little knowledge of electronics.     
• Off line Telephone tester - Here is a circuit of an off-line telephone tester which does not require any telephone line for testing a telephone instrument. The circuit is so simple that it can be easily assembled even by a novice having very little knowledge of electronics. This circuit provice the line current, sign signal and audio interface.     
• Telephone line monitor - detects if there is another telephone connected to the line, if there is a short or an open line     
• Telephone In-Use Indicator, Telephone Ringer and The Surfers Preserver - This Phone Ringer circuit will work with any ordinary phone including older bell ringer types. The circuit rings the phone in a completely realistic manner until someone answers. When the receiver is lifted the user hears the audio of your choice. DC current is passed through the phone to activate the phone?s electronics.     
   

• Remote controlling using telephone

• Phone Remote System - a telephone interface that allows the householder to give instructions to appliances from outside, application note from SGS-Thomson     
• Remote control using telephone - Here is a teleremote 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 digits 1 through 9 of DTMF the telephone key-pad). The telephone can be used to switch on or switch off the appliances also while being used for normal conversation.     
• Remote control using telephone - This is a teleremote circuit which enables switching ?on? and ?off? of appliances through telephone lines. It can be used to switch appliances from any distance, overcoming the limited range of infrared and radio remote controls.     
• Remote control using telephone - Here is a teleremote 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 digits 1 through 9 of the telephone key-pad). The DTMF signals on telephone instrument are used as control signals.     
• Telephone Line Relay Switch - Control 4 relays over your phone line. Dial up your phone from anywhere in the world, input your pin number then turn on or off any of 4 relays. Use the relays to control any devices you have in your house or office. The pin number is set by 4 on-board BCD rotary switches. The circuit has telephone line protection circuitry built-in (but not approved). Standard telephone line impedance termination can be customised by the user for their own particular country if they want to get better impedance matching.     
   

• Telephone billing related circuits

• 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.     
   

• Telephone answering machines

• Building a telephone answering system - laboratory report     
   

• Telephone line switching and PBX functionality circuits

• 9-Line Telephone Sharer - This circuit is able to handle nine independent telephones (using a single telephone line pair) located at nine different locations, say, up to a distance of 100m from each other, for receiving and making outgoing calls, while maintaining conversation secrecy. This circuit is useful when a single telephone line is to be shared by more members residing in different rooms/apartments.     
• EE476 Final Project AT90LS8515 PBX (Private Branch Exchange) - A project documentation that describes construction of a 4 line telephone systems with full signaling and switching functions similar to those of the central office systems.     
• Telephone "distinctive ring" switcher - zipper demo file from     
   

• Parallel phone secrecy circuits

• Having secrecy in parallel telephones - Often a need arises for connection of two telephone instruments in parallel to one line. But it creates quite a few problems in their proper performance, such as overloading and overhearing of the conversation by an undesired person. In order to eliminate all such problems and get a clear reception, a simple scheme is presented here.     
• Parallel Telephones with Secrecy - enable the incoming ring to be heard at both the ends and any one time, only one telephone is connected to the line     
• Telephone In-Use Indicator, Telephone Ringer and The Surfers Preserver - The Surfers Preserver is a simple device that prevents other phones in the house from disrupting your critical Internet session by disconnecting them from the line while you surf! The circuit is also useful in preventing eavesdropping from other extensions since other phones are "dead" until you hang up. The circuit wires in series with either of the offending phone?s wires (red or green) and it is small enough to tuck behind the wall cover plate.     
   

• Telephone headset circuits

• Telephone Headgear - A compact, inexpensive and low component count telecom head- set 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.     
   

• Misc telephone accessories

• Telephone In-Use Indicator, Telephone Ringer and The Surfers Preserver     
   

• Intercom circuits using normal telephones

• 2-Line Intercom-Cum-Telephone Line Changeover Circuit - The circuit presented here can be used for connecting two telephones in parallel and also as a 2-line intercom.     
• 2-Line Intercom-Cum-Telephone Line Changeover Circuit - The circuit presented here can be used for connecting two telephones in parallel and also as a 2-line intercom.     
• Creating Your Own Telephone Network - you can easily create your own intercom system using two telephones, a 9-volt battery (or some other simple power supply) and a 300-ohm resistor     
• Fax to Faxmodem interface circuit - can be also used as telephone intercom circuit or connecting two modems together     
• 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.     
• 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.     
• Using the Comrex HotLine or Vector on a Dry Pair - how to use simple pair of wires with no voltage, ringing signals to interconnect normal telephone line devices     
• Use old telephones as intercom     
   

• Surge protection

• Telephone line surge protection - information and circuits     
• Telephone line surge protector circuit - also archived at     
   

• Telephone transmitters

• FM Telephone Transmitter     
• Phone-bug - A simple transmitter that is powered from the phoneline, zipped file     
• Wireless Phone Jack - report what's inside it     
   

• Misc telephone circuits

• Circuit provides message on disabled phone line - play a prerecorded message into any phone on the line when its receiver goes off-hook     
• Fax saver cuts wear, tear, and power - less than $20 to cut wear and tear on your fax machine while saving power, circuit intercepts the incoming ring signal and powers up the fax machine in time to receive the fax and then turns off the fax machine after a predetermined time and awaits the next incoming fax     
• Telephone-related ASCII Schematics - wide collection of telephone circuits     
• Telephone Ringer using 556 dual timers - Using modulated rectangular waves of different time periods, The circuit presented here produces ringing tones similar to those produced by a telephone.     

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