No. 14 |
PAGE No. 34
A New Magneto Table Telephone
During 1935 the Ericsson Company introduced entirely new designs of moulded case type table and wall telephones suitable for auto/C.B. working. These instruments had the outward appearance shown in Fig. 1 & 2.
The popularity of this type of one piece moulded case was immediately apparent and further developments were subsequently undertaken with a view to increasing the scope of this type of telephone. Certain improvements in transmission and reception technique had become available during this period, and these improvements were incorporated in the new range of instruments.
The outcome of these further developments, which were undertaken in collaboration with the engineers of the British Post Office, was a type of telephone which can be used for many purposes by interchanging a few pieces of standard apparatus. This new type is now adopted and standardized by the British Post Office.
The main features of the new design auto/C.B. table telephone are improved transmission efficiency of approximately
1 d.b. above the British Post Office standard fixed for telephone No. 162 and bell set
No. 25, whilst reception is equal, and the inclusion of a new anti-side-tone induction coil providing much better side-tone conditions. Besides the foregoing improvements several key units were devised which can be added to the standard instrument when extension and operator-recall facilities are required. A further convenience was the provision in the telephone base of a sliding tray carrying a writing pad intended as a ready reference for the subscriber’s personal use. Fig. 3 & 4 show views of this telephone and its outstanding improvements.
This small generator was found to be eminently suitable for inclusion in the newest type moulded telephone case as used on the auto/C.B. telephones mentioned above, consequently further developments have resulted in a type of table telephone suitable for magneto working which is small in size and weight and at the same time pleasing in appearance.
The new magneto telephone is illustrated in Fig. 8 (Telephone N2120). The standard auto/C.B. moulded case is used, and in addition to being a cover for the components, provides a cradle for the moulded micro-telephone. A metal base plate carries all the internal apparatus and is completely detachable from the case-work. This base with components is illustrated in Fig. 9. On it are a condenser, induction coil, generator, ringer, ringer gongs, cradle switch springset and cord connection block. The condenser is, of course, only required in particular instances and is not fitted in standard
magneto telephones. The illustration, however, shows that space has been provided for its inclusion.
The underside of the base plate is shown in Fig. 10 and illustrates the means provided for giving easy access to the generator
cut-out and to the cord terminal block. It will be seen that subsidiary cover plates provided with captive fixing are employed, so that it is only necessary to remove these for immediate access to the cord connections and generator cut-out.
Last revised: October 14, 2019