Smartvox Labs

Smartvox Labs

Your accessible Learning Resource

Voice over IP | SIP | Linux | IP Networks | Electronics | Microcontrollers | IoT

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Technology Solutions

From fundamental concepts to practical examples; for VoIP, SIP, Arduino and more, we’re here help at every step.

VoIP and Telecoms

An archive of articles looking at Voice over IP using the SIP protocol. Wide ranging and with a special focus on OpenSIPS.

System Administration

A small collection of articles covering topics that may be of interest to network and system administrators.

Microcontrollers

Recently introduced, these articles explore some themes involving Arduino microcontrollers and peripherals.

Archive

Older articles which may no longer be very relevant are offloaded into the archive, but who knows – maybe they’re still useful.

Meet the Author

My enthusiasm for electronics started when I was still at school. I taught myself from books, magazines such as Electronics Today International (ETI) and with help from friends. I built a synthesiser in about 1974 and a great friend with a gift for music, especially keyboards, put it through its paces in various bands for several years to follow.

After qualifying in architecture, I somehow got heavily into software development and had a fantastic job writing programs simulating heat flows in buildings to allow engineers to size the building services plant and predict the energy use of the heating and air conditioning systems. After about 10 years I moved into telephony. It allowed me to combine my interests in electronics with my skills as a programmer. I’ve programmed in Fortran, C, C++, Pascal, PHP, Python, bash scripts and a few special purpose languages.

In the final 15 years of my career, I worked mainly with Voice over IP (VoIP), especially based around open source projects like Asterisk and OpenSIPS. Analysing and understanding SIP traces was at the heart of this work. Now retired and pleased to no longer be staring at SIP traces, I’m trying to keep the brain cells active by dumping some of the old knowledge here and building Arduino projects for fun.

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“The route headers and record route headers always confused me. This article has cleared up so much mess from my head. Thanks a ton!”

Anirudh

Latest Articles

  • Interrupt Timer for UNO WiFi Rev2 and other ATmega4809 units

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    John Quick

    The usual interrupt timer libraries and examples may not work on the Arduino UNO WiFi Rev2 and Nano Every because they use the ATmega4809 processor. So here is a quick and simple example showing how to use one of the inbuilt timers (TCB0) to toggle a variable that can be…

  • Caller ID in SIP

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    John Quick

    Equipment receiving calls, whether a humble handset or a sophisticated Call centre ACD system, likes to know the identity of the caller. It may simply display the caller’s number on an LCD display, look it up in a directory so the caller’s name can be displayed or pre-populate a screen…

  • Testing the NRF24L01 with Arduino Nano 33

    Testing the NRF24L01 with Arduino Nano 33

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    John Quick

    Summary NRF24L01 modules, because of their low cost, are an appealing option for data transmission over modest distances. They are best suited to unobstructed “line-of-sight” transmission, but one might hope at least to reach an adjacent room indoors. Here, I describe my experience testing a pair of NRF24L01 modules, each…

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