Telefunken logo

Like Siemens, the German company Telefunken (often shortened in documents to TFK) was founded in 1903 to develop products for the early telegraph. Also like Siemens it has diversified and grown into a major international player in the fields of consumer electronics and industrial goods.

Telefunken has been manufacturing semiconductors since the 1940s. Its devices rarely bear the company's rather nice logo, usually only the letters TFK.

The early history of Telefunken semiconductor manufacture has been comprehensively documented by Mark Burgess. There is little point in me repeating information that he provides, so this page is just a display of early TFK devices. I have a few original data documents for them, including the 'Telefunken Ausgabe', a booklet from 1959 that covers diodes and transistors.

I am seeking to buy or trade for certain germanium transistors and diodes made by Telefunken. Details are given below. I also want to find original data sheets for many of their devices.

If you know about these transistors, or have have some for sale or trade, please

Ich suche, die Germaniumtransistoren zu kaufen, die von Telefunken im Jahren 1950's und 1960's hergestellt werden. Ich suche nach den Transistoren, die nachstehend aufgeführt werden. Ich möchte auch ursprüngliche Leistungsblätter für sie kaufen.

Wenn Sie in diesen Transistoren auskennen oder haben, einiges für Verkauf oder Handel zu haben, in Verbindung.

Telefunken ED702e diode

Mark's research indicates that Telefunken manufactured silicon radar diodes such as this type ED702e from 1943 to 1944. Research in Leubus, now Lubiąż in Poland, had to be abandoned as the Soviet army advanced in 1944 causing the laboratory to be evacuated.

Telefunken microwave diodes

Telefunken made other microwave diodes. I have seen examples of silicon (?) types

Telefunken OA150 diodes

According to Mark, the first post-war semiconductor products from Telefunken were germanium point-contact diodes types OA150, OA159, OA160, OA161, OA172 and OA173. Early versions of these use an axial glass form with a decal around it bearing the Telefunken logo as well as the part number.

Telefunken OA diodes

I am looking for examples of OA159 and OA173 with such decals. If you know where I might get some, please

Telefunken OA161 diode

Later versions are painted black with white lettering and just the letters TFK rather than the logo.

Telefunken OA154Q diode quartet

Telefunken made more early diodes in the OA series. The 1959 'Ausgabe' lists:

Telefunken OA180 diode

There is also a type OA182B, which is a quad bridge of OA182 encapsulated in a plastic block.

I have also come across a miniature glass type OA460, for which I have no data.

Telefunken point-contact transistors

Telefunken experimented with germanium point-contact transistors, and may have exhibited some of them at trade shows, but these were not commercialised. The only one for which I know a part number is the GC1.

I am very interested to obtain such transistors. If you know about them, or others of Telefunken's earliest semiconductors, or have have some for sale or trade, please

Telefunken OC601

Telefunken then moved on to junction transistors, starting with the types OC601 and OC602 in 1954. The first versions of these used a flat case as shown in my image, unique in bearing the full Telefunken logo.

I am very interested to buy or trade for the flat-case OC601 and OC602. If you know where I can obtain them, or have have some for sale or trade, please

Telefunken OC602

By 1955 Telefunken had adopted a cylindrical glass tube similar to the VASCA SO-2 encapsulation familiar from the Mullard OC71 etc.

I am looking for OC601. If you know where I can obtain any, or have have some for sale or trade, please

Telefunken OC604 Telefunken OC603

Next came the AF amplifier types OC603 and OC604 in 1955 using the black glass capsule. I have some OC603 sealed inside original cartons as in the image.

Telefunken OC604SPEZ Telefunken OC602SPEZ

An oddity in the Telefunken range is that the glass tube types OC602 and OC604 exist in physically longer versions enclosed in a small metal heatsink and distinguished by the suffix 'SPEZ' (for 'spezial' presumably). My image of the OC602SPEZ shows two forms, one just a metal tube around the glass, the other with a metal fin that can be bolted onto further heatsink material.

Telefunken OD604

Again according to Mark, in late 1955 Telefunken showed their first power transistor, the OD604. This is an oddity. Like many early attempts to increase power dissipation it clamps a metal heatsink around a transistor in a smaller encapsulation. This was the first of several idiosyncratic power transistor designs from Telefunken.

Telefunken OD603

Telefunken subsequently issued several power transistors in a squat cylindrical outline with three leads issuing from a hole in the baseplate. The first was the OD603, an AF output type. Oddly, this seems to have been issued in 1958, several years after OD604.

The image shows unpainted and grey-painted examples. There exist also black-painted versions, possibly the earliest, some with an evacuation port on top. Furthermore, the device may have several maximum-voltage values and this is sometimes indicated by either a suffix or a number printed on the body.

Telefunken ALZ10

The ALZ10, an RF power amplifier, used the same outline. I'm not sure when this was first issued but it is listed in a 1964 databook: 'RIM Bastelbuch' by Radio Riem, a Munich company.

Telefunken AUZ11 Telefunken AUZ11D

The AUZ11 is a power switching transistor. Again I'm not sure when this was first issued but it is listed in the 1962 D.A.T.A. book 'Transistor Characteristics Tabulation' and the 1964 'Telefunken Handbuch: Transistoren'. There is a lower-speed variant, AUZ11D.

Telefunken OD605

The last in the idiosyncratic trio of OD series power transistors is the OD605, a black-painted cylindrical type larger than the OD604 and capable of 15 Watts dissipation.

I am interested to buy or trade for examples of OD605. If you know where I can obtain any, or have have some for sale or trade, please

Telefunken OC612

The OC series continued with the group OC612 to OC615, all RF amplifiers using the SO-2 glass capsule.


The rare type OC611 is believed to be an RF type although it does not appear in data books. It uses the SO-2 glass capsule.

I am interested to buy or trade for examples of OC611. If you know where I can obtain any, or have have some for sale or trade, please

Telefunken OC624

The 1959 Ausgabe also includes a triplet OC622 to OC624 of miniature AF transistors for use in hearing aids:

I am looking for examples of OC622 and OC623. If you know where I can obtain them, or have have some for sale or trade, please

OC6015 transistor

Thanks to Horst in Germany I have this unusual OC6015. Radiomuseum shows one and states that it only exists as development samples, and it is possibly a selected type of OC615 for Sennheiser.


There exists another rare type: the OC6016. The superb radiomuseum site has images of it, strangely in two different outlines: the small SO2 glass cylinder, and the bespoke metal power outline used by OD603 etc.

I am looking for examples of OC6016. If you know where I can obtain any, or have have some for sale or trade, please

Telefunken went on to manufacture many germanium devices in the standard pro-Electron series AA (diodes), AC, AD and AF. I don't have an exhaustive list, but the D.A.T.A. books 'Semiconductor Diode & Rectifier Characteristics Tabulation 1961 vol VII' and 'Transistor Characteristics Tabulation 1962 Vol XII' include early ones:

I have quite a few more later AC and AF types, and there are also germanium power transistors in the AD series.

Telefunken AA111

TFK made germanium diodes in the AA series:

as well as second-sourcing some such as AA119 and AA123.

Telefunken AAY18

In addition to single diodes, TFK made several quadruple diode types such as this AAY18. These are intended for use in modulators. They look like they are simply sets of normal miniature glass-bodied diodes potted in plastic.

Telefunken AC150

Many of the low-power transistors with the AC or AF prefix are in the tall TO-18-long (non-standard) outline such as this AC150.

Telefunken AC188K

Some types are embedded in an aluminium block heatsink like this AC188K (itself rivetted to an aluminium plate). These often have a suffix K for 'Kühlkörper' but I have a number of AC117 with heatsink that do not.

Telefunken AC106 Telefunken AC105

The 1959 Ausgabe includes AC105 in the SO-2 glass tube with heatsink fin, like the 'SPEZ' types, although 'Telefunken Halbleiter' 1959 lists it with no fin. Both publications describe it as an IF amplifier but later documents change that to an AF output transistor. It is possible this was a confusion with AF105, an IF type that has the SO-2 glass body but without the fin.

The slightly later and higher-gain AC106 is also an AF output type in the finned outline.

TFK ASZ30 wanted

So do the ACZ10, the AFZ10 and the ASZ10. The ASZ30 (shown) has the glass body but no heatsink fin. I am looking for examples of all of these types except ASZ30. If you know where I can obtain any, or have have some for sale or trade, please

I don't intend to show them, but of course Telefunken went on to issue many silicon transistors and diodes.