RESOURCES

A primer on the tube era and it's history (by Oliver Archut) can be found at TAB-Funkenwerk.
Additional info (partly overlapping) is here, another one here.
The documentation of all gear for radio and TV broadcast was contained in the so-called Braunbuch ("brown book"); some of the more interesting excerpts are hosted at the IRT website. An table of key specifications of the West German amplifier types available in the 1950's is given in this list.
Historical information about the different manufacturers from the 1930's to the 1960's (in German) can be found at Johannes Brüning's Funkstunde.

A huge archive of documentation for modules from both tube and solid state era - including components such as transformers, proprietary op-amp's etc. - is at the Kubarth website.

A good source (if in German) for the developement in East Germany (GDR) is this article by Wolfgang Hoeg. Info and documentation about specific models is provided by Udo Heusinger and at radiomusem.org. Previously much underrated, some modules have been increasing in popularity…

The Atomheart-Studio has great info & pictures about GDR based gear, but also Western solid state designs of Siemens SITRAL (see below) and WSW ("Wiener Schwachstrom-Werke" = Vienna Low Current Plant). The latter was an Austrian Siemens company and will not be covered here except for this link.
A German division of Siemens I shall mention briefly is Klangfilm - the direct translation ("sound film") indicates which market the company mainly produced for; they did, however, make a few active EQ's for mixing consoles that used the V72 standard. This site has fairly comprehensive information, along with some books, even (if in German language, of course).

Lastly, here's a rare find from the website of the DRA (= Deutsches Rundfunkarchiv, "German Broadcast Archive") that I recently came across by chance:
A super comprehensive list of every little type of gear or accessory for West German radio or TV that you could think of, ranging from the 1930's to the 1980's - in the format of an Excel-Table (sic!). So it's not limited to modules for installations or mixing consoles, but also includes microphones, battery supplies, cutters and pickups for wax or vinyl, magnetic tape gear, speaker cabinets, measurement devices, and so forth.
It's a kind of meta file, pointing to the actual physical folders you'd have to look into for the documentation of a particular unit. The very folder designations, since merely referring to an in-house archive, are not relevant here; the value of this document rather lies in the extensive overview of things. The colums of interest are:
- Gruppe (= group, denoting the type of device - see paragraph below)
- Nummer ( = number - dto)
- Bezeichnung ( = designation / description)
- Quelle (= source, meaning the company or institution providing the documentation)
- Ausgabe-Datum (= date of issue, meaning the date it was first published)


NAMES & ABBREVIATIONS

Besides types and manufacturers (covered in greater detail in the chapters following), there are a number of institutions which are mostly referred to in abbreviation:

RRG - Reichsrundfunkgesellschaft (= Broadcast Society of the German Reich), responsible for research and developement from 1928 until end of World War II. Their designs were built by several companies like Maihak, Siemens, Telefunken and others.
RFZ - Rundfunk- und Fernsehtechnisches Zentralamt (= Radio and TV Central Technical Office), responsible for all research and developement in East Germany (GDR) after World War II
It is sometimes confused with the label "RFT" (Rundfunk- und Fernmeldetechnik = Radio and Telecommunication Engineering), which was a common brand of devices, parts or even just electronic componets for audio and video technology, geared towards both consumer and professional applications in the GDR.
NWDR - Nordwestdeutscher Rundfunk (= North West German Radio). Until the founding of a dedicated institution (see below), they did a major part of audio research and developement in West Germany (FRG) in the early times after World War II
IRT - Institut für Rundfunktechnik (= Broadcast Technology Institute), founded by all West German broadcast stations in the 1950's, to centralize research & developement. In contrast to the eastern RFZ, the IRT didn't come up with specific designs of gear themselves; they rather introduced a catalogue of technical requirements ("Pflichtenheft") to be met by any piece of gear that was going to be used in the state-owned TV and radio stations.

… and some trivia - the abbreviations for the two parts of Germany we had between 1948/49 and 1990:
FRG = Federal Republic of Germany ("West")
GDR = German Democratic Republic ("East")


Types And Numbering

The labelling of almost any type of modules or other gear consisted of an initial letter plus a two- or three-digital number, sometimes followed by a suffix denoting a revision.

For both tube and solid state gear, the modules of most interest today start with the following letters:
U - meter / meter driver, dynamics processor, limiter/talkback amp combination, etc. (only used in the FRG; the GDR models used "V")
V - any sort of amplifier
W - equalizer, filter, fader, panorama control, MS-matrix, studio monitor controller…

Some other designations (among many more) are:
H - Tone generator
M - microphone (also MD, MKH, KM, SM)
N - power supply
O - loudspeaker
R - recording or playback device

As for the origin of some of the letters:
- U stands for „Umformer“ (=Converter), probably focussing on the aspect of converting AC audio signals to as to feed a meter, limiter sidechain etc.
- V stands for „Verstärker“ (=Amplifier)
- W originally stands for „Widerstand“ (=Resistor). Back in the 1940’s, when the numbering came up, faders, panorama controls, MS decoders etc. as well as equalizers and filters were realized as entirely passive modules, so they were all put into this category rather than having dedicated letters each. (That being said, passive filters and EQ’s are not purely resistive, also containing capacitors and inductors, but anyway… ;-)
- M obviously stands for „Mikrofon“ (=Microphone), with the subcategories MD („Mikrofon/Dynamisch“ = dynamic mic), MKH („Mikrofon/Kondensator/Hochfrequenz“ = HF condenser mic), KM („Kleinmembran-Mikrofon“ = small diaphragm condensor), SM („Stereo-Mikrofon“ = stereo mic) etc.
- N stands for „Netzgerät“ (=power supply unit)


Beyond Broadcast

The very nature of the modular systems allowed for customization of frame size and even custom designs of modules for special applications. Thus, they were not only to be found in broadcast, but also in theaters, commercial recording or mastering studios.