An usb enabled military telephone switch for digital non-secure voice terminals or DNVTs (TA-1042), uses Raspberry Pi Pico.Designed by Nicks Knacks in United States of America
Update on production status: both RJ45 and Terminal Block in stock at long last, including the adapter boards. We have about 50 units of transformers remaining, after which the lead time is into 2024…Read More…
Update on production status: both RJ45 and Terminal Block in stock at long last, including the adapter boards. We have about 50 units of transformers remaining, after which the lead time is into 2024 unfortunately, so if you're debating now is the time :)
RJ45 to TA-1042 adapters: we now have a separate listing for RJ45 adapter boards. You should be able to order these in the same order as the switch.
Kit Version: the new kit version will require soldering the DC barrel jack and 8x transformers (and terminal blocks for that version). Video instructions are here, no written instructions yet sadly.
Is your TA-1042 military phone collecting dust or sorely missing its ability to dial other phones? Well you're in luck! This nifty little device can interface with 4 DNVT terminals and provide a Line Simulator mode or interface them with your computer over a custom USB protocol. All code and hardware are open source. The product page here has links to all relevant resources.
This is an entirely open source project, hardware by Rob Ruark and software by Nick Andre. Featured in this YouTube video, the first of a series covering this project.
Rob has an excellent writeup on his website here as well.
Firmware Version 0.31
The switch integrates with 4 DNVT phones. When powered up without a host program running, the switch operates in "Line Simulator" mode to demonstrate the capabilities. An indicator on the screen will show USB status (
n/c - not connected,
inact - usb device is enumerated but host program isn't running, and
activ - usb host program is running and switch will proxy requests to the computer.
Line Simulator Mode: This mode allows the user to dial any of the 4 phones using a simple dial plan (press key 1-4 for line 1-4). The remote phone will ring and connect. When the second phone hangs up, the phone will return to dial mode and can call another phone.
USB Mode: a host program is available that uses the libusb binary to interface with the phone over USB 1.1. This host program currently allows switching between multiple switches, but should be considered more of a proof of concept. Several future improvements are planned (support for an AWS service that will switch between phones, proxying the data to Asterisk, etc.).
The display provides:
There are four current options:
In addition you may order the boards directly from a manufacturer using the design files should you wish.
In addition, we have a few assembled "Blinkenlights" versions (the first version we produced) that we will list. These do NOT include a display and instead have a light array. They are also missing DIP switches for configuration, so will use the default settings, but they do look cool.
Note: terminal blocks expose 4 wires for each phone. RJ45 exposes two phone interfaces per port; they do not follow the standard 10/100 ethernet wiring so if you want to split them you'll need a custom jack. The cheapest solution is to hack the end off an old CAT5 or higher cable and follow the pinout below. We will provide TA-1042 to ethernet adapter boards in a separate listing which allows you to plug directly into a phone with RJ45 and daisy chain a second phone.
The pinout of each RJ45 jack is printed on the end PCBs for assembled units and is as follows:
|1||Orange-White||DNVT 2/4||Red||DNVT RCV/SWITCH XMIT|
|2||Orange||DNVT 2/4||Red||DNVT RCV/SWITCH XMIT|
|3||Green-White||DNVT 1/3||Black||DNVT XMT/SWITCH RCV|
|4||Blue||DNVT 1/3||Red||DNVT RCV/SWITCH XMIT|
|5||Blue-White||DNVT 1/3||Red||DNVT RCV/SWITCH XMIT|
|6||Green||DNVT 1/3||Black||DNVT XMT/SWITCH RCV|
|7||Brown-White||DNVT 2/4||Black||DNVT XMT/SWITCH RCV|
|8||Brown||DNVT 2/4||Black||DNVT XMT/SWITCH RCV|
The default choice is fully assembled RJ45 switch, which includes the following:
It's pretty fun. Wanted to try my hand at embedded development, and Rob is great at hardware. Also nobody has been able to figure out how to reverse engineer the DNVT protocol and implement it on hardware, so we thought we'd take a stab at it, and it works. So now these doorstops can be used again :)
For a complete write-up see Rob's site here.
For the fun backstory watch this YouTube video.
I'll record a more in-depth demo soon.
This device uses the RP2040/Pico PIO state machines to perform differential manchester encode/decode. As a result you won't be able to use this as is on the Pico W which requires 1 state machine for wifi.
This device will only support either 16 or 32 KHz operation at one time; as a result, if you want to use TA-1035s, you must set all phones to 16 KHz and all phones will operate at that rate. For some more illumination:
Also the USB PHY is 1.1 which is plenty of bandwidth for DNVT in interrupt polling but worth noting.
The estimated range of the total wire length switch to phone is on par/better than the DNVTs. We estimate about 4km total with CAT5 compliant cabling. The main limit is attenuation.
For more software details, please review the github link. This code currently runs on one of the two cores in a processing loop. The second core is currently used for display updates due to the time requirements for the i2c display readout, but a transition of i2c to the DMA facilities would free the second core for additional functionality.
If you have ideas or want to make a PR, feel free!
We're also investigating the development of a similar analog 8 port FXS device with autovon DTMF decode to interface analog telephones, which will include a radio interface which can be enabled instead of the 8th line.
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