A manufacturer of lab and industrial test equipment, based in Berlin. Projekt Electronik's connection to electronic music is that the company accepted a commission from Peter Baumann to build a large, highly customized modular synthesizer for Tangerine Dream in 1975. These modulars were built to Tangerine Dream's exacting and ever-changing specifications, and they grew as the band saw a need for more functions; allegedly some Projekt Elektronik employees were hired to travel with the band and build modules on the fly during tours.
The PE modular synths were physically based on the Moog format, but the power and backplane connections were different from the classic Moog models. In order to meet the demands of live performance, the modulars had an extensive system of normalled signal routing. The PE backplane carried a large number of control voltage and gate signals on its bus; most of the control voltage sources (LFOs, envelope generators, etc.) were default routed to a specific line on this bus. Modules that used these had arrays of toggle and rotary switches to select control voltage and gates from the bus. Some of the VCOs also had fixed offsets that could be added to an incoming control voltage at the flick of a switch, in order to play musical intervals and chords from a single control voltage. The analog sequencers had an unusual amount of flexibility; they allowed for steps and patterns to be lengthened, shortened or skipped, all at the flick of a switch. This capability was a key to Tangerine Dream's sound in the 1970s.
Projekt Elektronik eventually built two large modulars for the band. Baumann took one of them with him when he left the band in 1977; he used it extensively on his first two solo albums. Edgar Froese wound up in possession of the other one, and he continued to use it up until about 1985. Baumann eventually sold his to Chris Franke; it appears on the back cover of Franke's The London Concert album. Projekt Elektronik subsequently declined commissions from other bands to build more systems, although they continued for a while to help out TD members with replacement parts and subassemblies for the existing units. Projekt Elektronik is still in business, but it has long since departed the music industry, and now focuses once again on test equipment.
Here is a thread on Muff Wiggler with descriptions and an extensive gallery of photos of the Projekt Elektronik modulars.