Signaling and coding ( 26 ) :

• Basic signaling

• How Telephones Work: Calling Someone on the Telephone Network - information on signals you hear whan you make a call   
• ITU-T E-Series Recommendations Excerpts - telephone information tones   
• Telephony Dialing and Signaling Tones: North American Call Progress Tones (CPTs)   
• Telephone ringing circuits - how to detect ringing and how to make phones ring   
• What is Ringer Equivalence?   
   

• DTMF dialling

• Disassembly Of A Touch-tone Phone - what is inside modern telephone   
• DTMF - Most Of What You Wanted To Know   
• DTMF Encoding and Decoding In C   
• Generating DTMF tones using computer soundcard   
• Touch-Tone Information - information on touch tone standards   
• DTMF Encoding & Decoding: An application of The Goertzel Algorithm - This thesis was awarded the Nokia Telecommunications Electronic Engineering Award for the Best Final Year Thesis in the Faculty of Science and Technology for the year 1994.   
• Sample stereo DTMF tones   
   

• Called ID

• Caller ID circuits and information - information and circuits for different systems used USA and Finland   
• Caller ID Links - lots of links to web Sites related to caller ID   
• Caller Identification - What Standards are Involved?   
• Computer Caller ID FAQ   
• FCC Caller ID page - general info nad FAQ   
• Frequently Asked Questions About Caller-ID   
• FX602 Calling Line Identifier IC - for deconding called ID systems used in USA and UK, datasheet has example circuits   
• Guidelines for implementation caller ID service in Finland (GFI9702) - information about DTMF based caller ID system in use in Finland   
• UK Caller ID FAQ homepage - information on setting caller ID system on PC   
   

• Audio signal coding

• Companding systems used in telephone PCM systems - A-law and my-law   
• Mu-Law Companding - A companding operation compresses dynamic range on encode and expands dynamic range on decode.   
   

• Misc

• Ensuring Voice Quality with Adequate Tail Length - Designers who worked on the POTS never dreamed of the challenges facing those working on next generation telecommunications equipment. Today's engineers live in the digital world where equipment designs are required to codify, compress, cancel echo, control jitter and loss, packetize, switch, route, and bill, and do it all more quickly and efficiently than their competitors. It is easy to lose sight of the need to provide a quality voice connection when the principal design goal is to maximize the volume of data the device can handle. Given these concerns, worrying about the length of the circuit tail delay in an echo-cancellation algorithm seems downright old fashioned and low on the design requirements list. But failure to appreciate tail delay will adversely affect voice quality.   
• E-Series Recommendations Excerpts   
• How message waiting lights work - description of different message waiting light systems   

 back to : Links >> Electronic Circuits >> Telephone Technology