Rob Ruark and Nick Andre Reverse Engineer Classic Military Telephones — and Build a Modern Switch

Military surplus Digital Non-secure Voice Terminals can live a new life, on a four-line switch powered by a Raspberry Pi Pico.

Vintage communications enthusiasts Rob Ruark and Nick Andre have been hard at work reverse engineering a military phone — and have built a compatible telephone switch, powered by a Raspberry Pi Pico, for any civilians interested in getting the devices up and running again.

“For an awkward period between the era of analog telephones and VOIP telephony, digital field telephones connected by twisted pair wires carrying unframed differential Manchester-encoded CVSD (Continuously Variable Slope Delta) modulated audio found use with the US military and NATO allies. These are DNVTs (Digital Non-secure Voice Terminals),” Ruark explains of the project.

“I’ve always through that field telephones are neat. In July 2022, these phones happened to come up in a conversation with my friend Nick Andre who was also interested in trying to get these phones working with a modern system.”

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