Although be a bit fussy, there are some rank amateurs out there too! Some examples of good quality sources: There are quite a few sites on the internet with some good hints on repairs and maintenance. Some components may require soldering skills as well. Although sometimes a bit "fiddly", many parts can be removed and replaced fairly easily with basic tools (screwdrivers, pliers etc). The majority of analogue dial telephones (and related CB and magneto models) are repairable. In the example below, the battery connects between 1 and 8 on the phone's internal terminal strip but in a similar model they are 1 and 10. Beware there are several models of 300/400 series Bakelite magneto phones and in some cases the connections differ. ![]() Connect L1 and L2 to each end, attach the battery at one end as discussed but run a third wire between terminals 4 (or equivalent) to power both ends. This is also the easiest way to test the operation of magneto telephones. 50m) a single 1.5V cell and three wires will work. To connect two instruments for demonstration purposes or very short distances (e.g. In some very early types the bell was permanently across the generator and rang each time but, as with the Commonwealth Ericsson, some models also provided a disconnect button. This automatically disconnects the bell set when the generator is turned. In the 334 example above, note the changeover switch on the generator. There was a debate on one forum about whether the local bells should ring when ringing out with the magneto generator. ![]() ![]() When signalling, remember to leave the handset on while ringing out, then pick up to listen and speak. In the circuit below the battery connects at the terminal strip between terminals 1 & 4, and that's it. circuit below, simply connect L1 and L2 to line and provide a small battery (1.5-3V) at each end. Magneto instruments can easily be set up as a simple point-to-point intercom system. for example the 1920s Stromberg Carlson as shown below. In earlier, timber, wall models the battery was usually inside the main telephone. In early table mounted magneto telephones and also later Bakelite models, the local battery was usually contained in a skirting mounted, timber, metal or Bakelite box. Magneto telephones share similar operating principles to CB 'phones with the exceptions of magneto generator signalling and a local battery (usually 3V) to power the transmitter which, in turn, required a different ASTIC (voice coil). The last magneto telephone exchange closed in WA in 1985 so, at the time of writing (2020), there are still quite a few telephones around in private collections and for sale. The circuit current paths of a 300 type phone can be viewed on the attached PDF document below. It is identical to the CB version but with the addition of a rotary dial in place of the straps on the dial cord term. The final circuit is of a 332 automatic telephone. The manual exchange detects line current when the handset is lifted and alerts the operator. there are no signalling components per se. Note the absence of a local battery and generator and different type of ASTIC (anti-sidetone induction coil). The major parts of the circuit (from L-R) are line connections L1 and L2, bell circuit (1000 ohm bell and capacitor), switch-hooks, dial terminal strip, ASTIC, handset cord and handset (receiver at top). The second example is a 332 CB telephone. This website has kindly published an old PMG document on magneto telephone operation: ![]() Although, curiously, the bell symbols are markedly different. Other components are similar to CB/dial 'phones, below. The magneto generator is represented by the loop shaped symbol and changeover switch connected between terminals 1 and 9. The battery voltage was typically 3 volts and its role was to power the transmitter (connected between terminals M and MR). Note the battery (usually located in a separate wall mounted box) is connected between terminals 1 and 4 on the external terminal strip (LH side of diagram). The first example above is a local battery - magneto telephone 334MT.
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