F-3090

The F-3090 is a military telephone multiplex system with one carrier channel, for short two-wire lines, made in two versions, F-3090-1 and F-3090-2, made by Electromagnetica in Bucharest [1]. It was among the first telephone multiplex systems designed by ICSITA and made by Electromagnetica’s Special Production Factory, from the late 1970s [1]. The modernised generation, with modular mechanics standardised by ICSITA, comprised the F-3091 and F-3031 [1].

It transmitted the 300–2700 Hz band, chosen for compatibility with the imported equipment in service; on two wires it formed one carrier channel besides the physical one, with up to 5.5–6.0 Np attenuation, and an F-3090-1 and an F-3090-2 together gave the physical channel and two carrier channels on one two-wire circuit, separated by built-in line filters [2]. With the F-3140 it also carried a telegraph channel, the telephone band narrowing to 300–2500 Hz; it could also work on four wires, had a crystal-oven carrier generator, modular boxes and an aluminium-profile case, and worked from −10 to +50 °C [2]. It was later redesigned as the F-3091 [3].