A Custom Radio And Telephone System For Glider Winch Operators

March 1, 2022 by Robin Kearey 16 Comments

While gliding might be the most calm and peaceful way of moving through the air, launching a glider is a rather noisy and violent process. Although electric winches do exist, most airfields use big V8-powered machines to get their gliders airborne. [Peter Turczak] noticed that the winch operators at his airfield often had to juggle multiple communication channels while pressing buttons and moving levers, all with the deafening roar of a combustion engine right next to them. To make their life easier, he built a single communication device that combines multiple radio inputs and an analog telephone .

A stack of circuit boards next to an old phone ringer — The inside of the cabinet. Note the classic phone ringer

The main user interface is a sturdy headset that dampens engine noise significantly. This headset is connected to a cabinet that contains several modules connecting to different audio sources: an analog telephone line, an aircraft radio receiver, a PMR handheld radio, and even a music source in case the other lines are quiet. The system contains automatic switchover circuits based on a priority system, ensuring that important messages are never missed.

The electronic design is based on classic analog components like NE5532 and TL084 op amps, all mounted on small, custom-made PCBs. Audio transformers are used to avoid ground loops between the various signal sources while relays mute sources that are not prioritized. To ensure seamless compatibility with the telephone network, [Peter] used components from old desk phones, including line transformers, a DTMF keypad and even a mechanical ringer. His blog post is full of details that will be of interest to anyone working with op amps and audio, such as how to stabilize an amplifier that has significant wiring capacitance on its input.

At heart this whole project is “just” an audio mixer, although optimized for a very specific purpose. But designing even a simple mixer is by no means an easy task, as we reported a few years back. If you’re more into winches, you’ll be delighted to find that smaller ones can also be used for sledding and even wakeboarding.

A Rotary Phone As A Computer Peripheral

November 26, 2021 by Jenny List 5 Comments

It’s an age-old conundrum for anyone working with retro hardware: preserve its original condition or not? The answer depends so often on a complex mix of how rare, obsolete or unusable the device is in its original form , and what the intended use for the device will be. For [Typhon Mind] who needed a novelty method of recording best wishes at a wedding through an old dial phone there was no need for it to be entirely original, so the solution was to turn it into a USB device for a host computer.

Out went the original circuitry, and in came a USB hub, a USB audio interface, and an Arduino. The original earpiece would suffice, but the microphone was replaced with a more modern one. The Arduino will register the cradle switch, and also power a set of LED addressable lights under the unit.

The result is a phone that retains all its looks, but has a new life as a PC peripheral. We’d venture to suggest that also using the Arduino to read the dial and produce DTMF tones might make it a valid peripheral for a VOIP application and complete the transformation, but that’s something that could be done at a later date. Maybe it could even be given a GSM makeover.