A Dial Phone SIPs Asterisk

An endless source of amusement for those of advancing years can come from handing a rotary phone to a teenager and asking them to dial a number with it. It’s rare for them to be stumped by a piece of technology, after all. [Mnutt]’s 4-year-old son had no such problems when he saw rotary phones at an art exhibition, so what was a parent to do but wire the phone to an Asterisk PBX with shortcut numbers for calls to family and such essential services as a joke line, MTA status, or even a K-pop song.

It’s possible to hook up a pulse dial phone with a SLIC module and a microcontroller, but in this case, a Grandstream SIP box did the trick. These are all-in-one devices that implement a SIP client with a physical connection, and older ones will talk to pulse dialers as well as the more usual tone dialing phones. The phone in question is a vintage American model. Writing this from Europe we were surprised to find a little simpler inside than its transatlantic counterparts of the same era.

An Asterisk install on a Raspberry Pi completed the project, and thus it became a matter of software configuration. It’s a useful run-through for Asterisk dilettantes, even if you haven’t got a 4-year-old. Perhaps you have an old payphone or two!

8 thoughts on “A Dial Phone SIPs Asterisk

    1. Yes I can use a Grandstream 802 and works perfectly with Sipgate. However just signed up to Community Fibre in London and they supply a Grandstream but locked with pulse dialling not activated and so unable to change. How stupid are these people.🤷

  1. SLIC = Subscriber Line Interface Card (not Module).[1]

    “Grandstream SIP box did the trick. These are all-in-one devices that implement a SIP client with a physical connection, and older ones will talk to pulse dialers as well as the more usual tone dialing phones.”

    The correct name for that device is a Voice over Internet Protocol Analog Telephone Adapter or VoIP ATA.[2] VoIP ATAs are the most cost effective way to connect one or a few subscriber stations (analog telephones) to a VoIP Private Branch Exchange (VoIP PBX).

    Another approach, especially when you need to service many analog telephones (assuming they are Dual Tone Multi-Frequency [DTMF]) Dialing, is to use one or more multi-channel Foreigm Exchange Station (FXS) PC card(s).[3]

    The project builder said, “I would have been able to attach the Grandstream adapter directly to the machine running the Asterisk server. But for the equipment I had, I ended up attaching the Grandstream to the Raspberry Pi in my son’s room, and having it bridge wifi to an old server under my desk running Asterisk.”

    I don’t understand that. A Raspberry Pi 4 or 5 can run the whole thing; the Asterisk VoIP PBX, PIPER Text-To-Speech (TTS), et-cetera. Just try to avoid using aggressive voice CODECs like G.729 (CS-ACELP; 8kbit/s); the G.721 (superseded by G.726; 32kbit/s) CODEC is a good choice.

    Hey, just for fun here’s a $42.99 off-the-shelf desktop analog rotary-dial telephone that emits DTMF tones when dialed![4] Watch the video of it in action.

    * References:

    1. Line Card


    2. Grandstream HT801 Single-Port Analog Telephone Adapter, 4.2 out of 5 stars 833 ratings, Amazon’s Choice Overall Pick, 500+ bought in past month, $38.00 ea.


    3. Foreign Exchange Service (telecommunications) – Circuit Interfaces


    4. TelPal Retro Single Line Corded Desk Telephone Classic Vintage Rotary Dial Hands Free Landline Phone for Home/Office/Hotel, Antique Phones for Seniors Gift (Black) 4.3 out of 5 stars 69 ratings $42.99


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