Desk telephone W 48
The desk phone W 48 was - after the desk phone W 46 , which was only produced briefly by the manufacturer SABA - the second German post-war telephone , which was developed in 1948 for the Deutsche Post in the western occupation zones (from 1950 Deutsche Bundespost ) and manufactured in very large numbers.
As with the previous models, the 36 model and the W 38 desk phone , Siemens & Halske played a key role in its design. In principle, the W 48 is just a further development of the W 38 of the Deutsche Reichspost . For many collectors and enthusiasts, the W 48 has become a classic among German telephones and the epitome of the "old telephone".
predecessor
In the 1930s, the company Siemens & Halske was commissioned by the Deutsche Reichspost to develop a new, cheaper to manufacture standard telephone, which should replace the previous standard model W 28 . This is how the forefather of the W 48 was born, the so-called Model 36 , which was presented at the Leipzig Spring Fair in 1936 . Due to technical inadequacies, however, it was not introduced by the Reichspost. Only the improved successor model W 38 from 1938 received Reichspost approval and was produced in large numbers from 1940.
On the outside, the 36 and W 38 models hardly differed: a solid version made of black Bakelite and a heavy steel base plate, a Bakelite fork and a large, ergonomically shaped telephone receiver . The structure of the base plates was completely different for the 36 and W 38 models; The 36 and 38 cases cannot be interchanged either. The alarm clock had two bells. Most parts of these two models, however, are identical. From around 1940, the bowls of the alarm clock were made of pressed glass in order to save metal that was important for the war effort. After the Second World War , the W 38 was produced unchanged in both parts of Germany; in East Germany the glass bells were retained. In contrast to the metal bell shells, glass bells produce a less beautiful, clinking, rattling sound.
In West Germany (1948) and East Germany (1958) the W 38 had slightly improved successors (W 48 and W 58 ). The only difference between the W 48 and the W 38 is the way the listener speaks. In the W 38 it is funnel-shaped, in the W 48 it is almost flat, since with the funnel-shaped version it was found that for hygienic reasons people were often speaking wrongly, making it difficult to understand the conversation partner. All parts of the 38 and 48 series are interchangeable.
development
From around 1950 almost all West German telephone manufacturers produced the W 48 under license for the Deutsche Bundespost , which did not sell the device, but only made it available to telephone customers for use for a fee. Just like the external shape, the technical interior of the W 48 has remained almost unchanged over the years. There were only minimal differences in design between the individual manufacturers; only the company SABA briefly built in around 1950 a rather unusual, self-constructed number switch with a finger-recess disc. There weren't the usual holes in this dial, but hemispherical indentations. However, this variant could not prevail because it was hardly usable for people with long fingernails.
Equipment, color, variants
As with the previous models, Model 36 and W 38 , the electrical and mechanical components of the W 48 were mounted on a metal base plate and freely wired with bound cable harnesses. In the course of time, the twin-coil alarm clock was replaced by a cheaper single-coil version. Different manufacturers produced different rotary number switches of the type NrS 38 under license, such as the NrS 38 M from Merk or the NrS 38 R built by Siemens in 1956 with an anti-reverse device, which was supposed to prevent a mechanical wrong selection.
Towards the end of the 1960s, the specimens that were overhauled or repaired in the telecommunications offices were quite often equipped with a newer design number switch (with a transparent plastic finger-hole disk) that did not match the overall appearance . However, these number switch types were never installed at the factory.
The first copies of the W 48 had a microphone speaker cap with only 22 circular holes, which were later expanded to 40 in order to improve the quality of communication. The device was initially delivered with a cotton-sheathed or plaited cord. At the customer's request, the Bundespost offered a stretchable, textile-coated cord as a special accessory, but the elastic band quickly tore when it was overstretched, so that it then remained on its full length of around 2 meters. From the 1960s, a stretchable plastic spiral cord was also offered as a special accessory, which was used for repairs until the 1980s.
As standard, a hearing protection rectifier made of two selenium diodes was installed in the telephone receiver to suppress the loud popping and crackling noises that z. B. emerged when operating the fork and also with the electromechanical switching technology ("bang protection"). The hybrid circuit for the back hearing loss has also been changed several times - especially for office equipment.
The standard color of the W 48 was black, but like the W 28 , W 38 and W 49 models , it was also available in ivory . The plastics of the ivory-colored devices were not very lightfast and moreover more fragile, which is why many devices of this color are damaged or faded today. Depending on the manufacturer, there were also clear color differences in the ivory-colored cases. Because the production of ivory-colored thermoset was more complex and expensive, the bright devices were considered a status symbol; they were only provided by the Federal Post Office for a surcharge and were more likely to be found in wealthy households as well as medical practices, law firms or hotels. The W 48 was very rarely available in other colors, e.g. B. in gray, brown or dark green. For training purposes for prospective telecommunications technicians, a transparent version was made from Plexiglas (later as a design replica by Reiner). These specimens are also rare.
If you find a colored device today, it is most likely a later painted copy or it comes from the new edition produced in the 1990s. You can recognize lacquered devices by the fact that the color of the dial of the number switch does not match (exceptions concern very rare ivory-colored extension units in their original state, as well as the light red replica unit from Reiner).
As a rule, the numbers on the carrier disk are white on the black models and green on the ivory models. While the metal shelves of the black devices are always black (with different painting processes), there is no uniform trend in the ivory-colored models. For example, Bosse, DFG, Reiner and SEL devices have silver-colored base plates in different paint finishes, while Krone has used a beige paint finish to match the case. Siemens has also often used original black base plates for ivory-colored models. The W48 is available for large and small telephone systems , equipped with an earth button , indicators and extension buttons for manual switching.
W 48a
While the circuitry and assembly structure of the W 48 standard models (W 48 oT) for the Bundespost remained unchanged, the W 48a indicator devices (W 48a uSz) were manufactured in different circuit and structure variants. The W 48a telephones are technically designed for an A2 connection . The flag was placed either in the middle or on the left, depending on the manufacturer and the presence of an earth button (mT). However, there were space problems due to the rather large alarm bowls. However, since you did not want to enlarge the housing of the earth key models with indicators, you had to make other changes: Either you built in a smaller alarm bowl (see photo), or you used two smaller bells or the indicator was placed in the middle , while a reduced earth button was fixed on the right side of the original bells by means of a metal rail. Sawing through a normal alarm bowl was also practiced by the manufacturer, whereby half an alarm bowl could no longer produce a bell sound.
| abbreviation | meaning |
|---|---|
| W 48 oT | without earth key |
| W 48 mT | with earth key |
| W 48a uSz | A2 circuit, switchable indicator |
| W 48a uSz mT | A2 circuit, switchable indicator, with earth button |
W 48 wall
For wall mounting, Deutsche Post offered the "W 48 wall", which, apart from a few differences, is identical in construction to the "W 38" wall-mounted device from 1938 and the "W 51" from 1951. The company Hagenuk from Kiel produced technical equipment with the identical W 49 (model name: Ti-Wa W 49) a model that could be converted from a table-top to a wall-mounted unit.
Under the name of the subscriber coin-operated telephone 55b (Tln Mü 55b) there was a W 48-like desktop coin-operated telephone for local calls . After the introduction of the clock rate for local calls, the commercial use of this table coin was prohibited in 1980, since with a payment of 20 pfennigs it was possible to make local calls for hours, which was at the expense of the subscriber who had to pay the post office in units of fees.
successor
Until the end of the 1960s, the W 48 remained the simple, reliable and inexpensive standard telephone of the Deutsche Bundespost. Since the devices were mostly loaned to the participants by the Post at the time, repairs were at the expense of the Post, so that they were interested in the most reliable and durable devices and less in additional convenience for the customer. Even minimal functional expansions, such as a volume control for the ringtone, have been dispensed with. The foreseeable end of the W 48 but was ushered in 1963, when the German Federal Post the telephone table apparatus 61 (FeTAp 61) introduced a technically and visually completely new, more manageable phone thermoplastic, impact-resistant ABS - plastic .
Since this new device was initially only available with and without an earth button , but not yet as a device for an A2 circuit , the models W 48a or W 49a were still required until 1967. It was not until the FeTAp 61 that the telephone in the Federal Republic of Germany turned from a luxury object into a natural object of daily use.
The W 48 today
The W 48 has not completely disappeared. Because of its formerly widespread use, it is still very well known and is now enjoying increasing popularity as a "classic telephone". They were already popular at the end of their service life in the 1970s and 1980s and were therefore often not disposed of by the post office but given to interested parties. Old originals are being restored and used again today. After the problem-free installation of a modern transistor speech capsule instead of the conventional carbon microphone (or a new carbon capsule from the 61 series devices), the speech quality corresponds fully to today's standard, although the back hearing loss (the attenuation of one's own voice) is somewhat worse due to the somewhat simpler speech circuit than with the 61 series successors.
By retrofitting a TAE plug, a W 48 can be operated without any problems on an analog telephone connection in the Deutsche Telekom telephone network . For operation on telephone systems that only support multi-frequency dialing (DTMF), an external pulse-to-DTMF converter to be plugged between the TAE socket and the W 48 or another analogue telephone system with pulse-to-DTMF conversion is required (operation as a subsystem ). The W 48 can also be operated on ISDN and other modern digital systems with an a / b converter (terminal adapter) capable of pulse selection . Various models of the Fritz! Box from the Berlin manufacturer AVM support, for example, the pulse dialing method on the analog connections, so that a W 48 can be connected directly. According to the support, the pulse dialing process is not a guaranteed feature of the Fritz! Boxes. In addition, support is generally no longer included in current Fritz! Boxes.
Another problem with modern, smaller telephone systems is that the ringing power supply is often too weak because it is designed for the electronic ringing of today's telephones. This is often not enough to supply the inductive electromechanical alternating current alarm clock of the W 48. In the simplest case, the ringing voltage (usually 24 volts) in many private branch exchanges is obtained from a separate transformer winding and thus inevitably corresponds to the frequency of 50 Hz common in the power grid. The W 48 alarm clock is suitable for a ringing current frequency of 25 Hz and 50 Hz, however, it rings less harmoniously at 50 Hz and tends to rattle or rattle if the setting is not correct. In addition to the FritzBox devices from AVM, some other telecommunications systems now also offer the option of setting the ringing current frequency on the analog connections to 25 Hz (Auerswald, Elmeg, Agfeo, Siemens HiCom 150).
In many cases, the number switches, which have become very gummy and worn over the years, have to be overhauled or replaced, because an imprecise pulse sequence, especially with modern telephone systems, can easily lead to wrong dialing. However, the 38-digit number switches, which are used in W 48 devices, can usually be overhauled without any problems through thorough cleaning and (economical) re-lubrication, provided that you have precision tools and the appropriate skill.
The Wilhelm Heibl Werke GmbH & Co. KG company has released a new edition of the W 48 with a modern interior for the 500th anniversary of the Post in the early 1990s. A replica of the W 48 is being made by Friedrich Reiner Telekommunikation . The W 48 is still available today as a new device in black and ivory (other special colors are also available) - equipped with a modern interior (copper-clad, etched Pertinax board with soldered-on components) and transistor speaker capsule.
