Roland System 100
The Roland System 100 was an analog semi-modular synthesizer manufactured by Japan's Roland Corporation, released in 1975 and manufactured until 1979.
The modules - the 101 synthesizer, 102 expander, 104 sequencer and 103 four-channel mixer with built-in spring reverb and mono fx send/return & the 109 speakers could be used independently, but there was no true modular flexibility, as with the later Roland System-100M and the Roland System 700. The component parts gave an expandable two-oscillator monosynth with sequencing, monitoring and effects capabilities. Each unit was independently powered so that there was no weakening of oscillator power due to complex patching. The 101 and 102 are internally normalised so they can be used without patching at all. Also, uniquely for the time, the 100 didn't have the oscillators "locked in" to fixed footages or pitches, which allows maximum flexibility for sound design. It can also be used with a MIDI-to-CV converter, as it supports the 1v/oct standard. More modules were apparently planned, but none were ever produced.
The System 100 is still sought-after due to its filter, sequencer and patching capabilities, though the oscillators can be unstable at the lower frequencies, the keyboard is prone to mis-triggering and double-triggering if not used regualrly, but generally these are very robust and reliable systems. The Roland SH-5 AND SH-7 are very similar in styling but both are complete keyboard units, as opposed to the modular System 100.
Notable use of the system was by Mute Records label head Daniel Miller who helped produce Depeche Mode's A Broken Frame and by Human League (MK1 incarnation) - the albums Reproduction and Travelogue used a large system 100 (1 x 101, 2 x 102, 2 x 104, 1 x 103) multitracked to provide nearly all the arrangements including drums and percussion. Vince Clarke is also a user: it can be heard on many of Erasure's albums including the "all analog" works post-1991. The K2 Plan (Shekhar Raj Dhain) has also used it extensively in a similar vein, multitracked and with the sequencer providing odd syncopations and effects. Joy Electric's The White Songbook album (2001) was created by using a System 100 exclusively.
References
http://www.vintagesynth.com/roland/sys100.shtml
http://www.synthmuseum.com/roland/rolsys10001.html
http://fa.utfs.org/diy/roland100/index.html (Download of service manuals, owners manuals, patch books)
http://nitrogen.synth.net/Roland/ Various pertinent circuits, mods, datsheets