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7 Articles

Homebrew Telephone Exchange Keeps The Family In Touch, In The House And Beyond

January 14, 2023 by 4 Comments

It doesn’t happen often, but every once in a while we stumble upon someone who has taken obsolete but really cool phone-switching equipment and built a private switched telephone in their garage or basement using it. This private analog phone exchange is not one of those, but it’s still a super cool build that’s probably about as ambitious as getting an old step-by-step or crossbar switch running.

Right up front, we’ll stipulate that there’s absolutely no practical reason to do something like this. And hacker [Jon Petter Skagmo] admits that this is very much a “because I can” project. The idea is to support a bunch of old landline phones distributed around the house, and beyond, in a sort of glorified intercom system. The private exchange is entirely scratch-built, with a PIC32 acting as the heart of the system, performing such tasks as DTMF decoding, generating ring voltage, and even providing a CAN bus interface to his home automation system.

The main board supports five line interface daughterboards, which connect each phone to the switch via an RJ11 jack. The interface does the work of detecting when a phone goes off-hook, and does the actual connection between any two phones. A separate, special interface card provides an auto-patch capability using an RDA1846S RF transceiver module; with it, [Jon Petter] can connect to any phone in the system from a UHF handy-talkie. Check out the video below for more on that — it’s pretty neat!

We just love everything about this overengineered project — it’s clearly a labor of love, and the fit and finish really reflect that. And even though it’s not strictly old school, POTS projects like this always put us in the mood to watch the “Speedy Cutover” video one more time.

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Ask Hackaday: With Landline Use In Decline, What’s To Be Done With The Local Loop?

October 12, 2020 by 100 Comments

Walking is great exercise, but it’s good for the mind too: it gives one time to observe and to think. At least that’s what I do on my daily walks, and being me, what I usually observe and think about is the local infrastructure along my route. Recently, I was surprised to see a number of telephone company cabinets lying open next to the sidewalk. Usually when you see an open box, there’s a telephone tech right there, working on the system. But these were wide open and unattended, which I thought was unusual.

I, of course, took the opportunity to check out the contents of these pedestals in detail. Looking at the hundreds of pairs of brightly colored wire all neatly terminated and obviously installed and maintained at great expense, I was left wondering why someone would leave such a valuable asset exposed to the elements. With traditional POTS, or plain old telephone service, on the decline, the world may no longer have much use for the millions of miles of copper cable feeding back to telco central offices (COs) anymore. But there’s got to be something this once-vital infrastructure is still good for, leading me to ask: what’s to be done with the local loop?

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Classic American Dial Phone Gets A GSM Makeover

April 18, 2018 by 14 Comments

For sturdy utilitarianism, there were few designs better than the Western Electric Model 500 desk phone. The 500 did one thing and did it well, and remained essentially unchanged from the mid-1940s until Touch Tone phones started appearing in the early 70s. That doesn’t mean it can’t have a place in the modern phone system, though, as long as you’re willing to convert it into a cellphone.

Luckily for [bicapitate], the Model 500 has plenty of room inside the case once the network interface is removed, because the new electronics take up a fair bit of space. There’s no build log per se, but the photo album makes it clear what’s going on. An Arduino reads the hook switch and dial pulses, while a Fona GSM module takes care of the cellular side of things. It looks like a small electret mic and a speaker replace the original transmitter and receiver. As a nice touch, the original ringer is used, but instead of trying to drive it electrically, [bicapitate] came up with a simple cam mechanism on a small motor. Driven at the right speed, the cam hooks the clapper arm, rings one bell, then releases it to let the clapper spring back to hit the other bell. Everything is powered by a LiPo, so it could be taken to the local coffee shop for some hipster hijinks.

We’ve seen similar retro-mods like this before using phones from all over the world; here’s a British take and one from Belgium, both using phones with equally classic lines.

[via r/arduino]

Classic British Phone Gets A Google Makeover

September 28, 2017 by 19 Comments

It may seem like an odd concept to younger readers, but there was once a time when people rented their phones rather than buying them outright. Accordingly, these phones were built like tanks, and seeing one of these sturdy classics of midcentury modern design can be a trip down memory lane for some of us. So retrofitting a retro phone with a Raspberry Pi and Google’s AIY seems like a natural project to tackle for nostalgia’s sake.

The phone that [Alasdair Allan] decided to hack was the iconic British desk telephone, the GPO-746, or at least a modern interpretation of the default rental phone from the late 60s through the 70s. But the phone’s looks were more important than its guts, which were stripped away to make room for the Raspberry Pi and Google AIY hat. [Alasdair] originally thought he’d interface the Pi to the rotary dial through DIOs, until he discovered the odd optical interface of the dialer — a mask rotates over a ring of photoresistors, one for each digit, exposing only one to light from an LED illuminated by a microswitch on the finger stop. The digital interface brings up the Google voice assistant, along with some realistic retro phone line sounds. It’s a work in progress, but you can see where [Alasdair] is in the video below.

If stuffing a Google Pi into a retro appliance sounds familiar, it might be this vintage intercom rebuild you have in mind, which [Alasdair] cites as inspiration for his build.

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Exposing Dinosaur Phone Insecurity With Software Defined Radio

June 5, 2017 by 74 Comments

Long before everyone had a smartphone or two, the implementation of a telephone was much stranger than today. Most telephones had real, physical buttons. Even more bizarrely, these phones were connected to other phones through physical wires. Weird, right? These were called “landlines”, a technology that shuffled off this mortal coil three or four years ago.

It gets even more bizarre. some phones were wireless — just like your smartphone — but they couldn’t get a signal more than a few hundred feet away from your house for some reason. These were ‘cordless telephones’. [Corrosive] has been working on deconstructing the security behind these cordless phones for a few years now and found these cordless phones aren’t secure at all.

The phone in question for this exploit is a standard 5.8 GHz cordless phone from Vtech. Conventional wisdom says these phones are reasonably secure — at least more so than the cordless phones from the 80s and 90s — because very few people have a duplex microwave transceiver sitting around. The HackRF is just that, and it only costs $300. This was bound to happen eventually.

This is really just an exploration of the radio system inside these cordless phones. After taking a HackRF to a cordless phone, [Corrosive] found the phone technically didn’t operate in the 5.8 GHz band. Control signals, such as pairing a handset to a base station, happened at 900 MHz. Here, a simple replay attack is enough to get the handset to ring. It gets worse: simply by looking at the 5.8 GHz band with a HackRF, [Corrosive] found an FM-modulated voice channel when the handset was on. That’s right: this phone transmits your voice without any encryption whatsoever.

This isn’t the first time [Corrosive] found a complete lack of security in cordless phones. A while ago, he was exploring the DECT 6.0 standard, a European cordless phone standard for PBX and VOIP. There was no security here, either. It would be chilling if landlines existed anymore.

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GSM To Landline Box Has A Creatively Soldered Cellphone Inside

January 22, 2013 by 26 Comments

gsm-to-landline-box-teardown

We don’t blame the manufacturer of this GSM to Landline converter box for not designing the thing from the ground-up. After all, quantities of scale have made dumb-cellphones available for next to nothing. But you have to admit that it’s interesting to see a fully populated cellphone board creatively soldered into a consumer product. It would be commonplace if made in your basement rather than being sold in a store.

[Anton] was using the box to add his analog house phones to the cell network. The signal strength at home is pretty low and this box offers an external antenna for better reception. He cracked open the case expecting to see a GSM modem and was surprised to see the cellphone board. It includes a battery backup, and has been soldered directly to the cables which interface with the main PCB using some SIL connectors. Those solder joints were done by hand directly to the pins of the SIM card slot and as well as all of the other important connection points.

Hackit: Why We Don’t Need Phone Numbers

September 4, 2009 by 72 Comments

do_we_need_phone_numbers

[digg=http://digg.com/software/Why_we_don_t_need_phone_numbers]We’re starting to think that phone numbers are deprecated; it may be time to integrate how we connect telephones with the new digital millennium. To get a firm grasp on this topic it is important to take a look at the reason we started using phone numbers, why we still use them, and the why’s and how’s of transitioning to a new system.

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