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The bottom part (frame) ot the set Push-button dialling mechanism 1. Common contact spring assembly 2. Slide 3. Switching bar Fig. 5 Cradle switch mechanism 1. Contact spring assembly 2. Arms 3. Return spring 4. Switching bar 5. Cradle key 6. Switching bar 7. Cradle buttons The signalling device of the telephone set, the bell, has in certain cases already been replaced by a tone ringer, either with a separate electroacoustic signal generator or with the receiver or microphone as the sound transmitter. The advantages of tone ringing are a more pleasant but at the same time more penetrating signal, and a unit that, from the design point of view, requires less space than a conventional bell. Apart from the advantages as regards function and quality, a design using modern electronic technology with integrated circuits also means a substantial reduction in the weight of the set. In connection with the centenary of the telephone and of LM Ericsson, the company introduced the first wholly electronic one-piece telephone set. The exterior of the set has the classical shape of ERICOFON. Mechanical design and construction The new telephone set, ERICOFON 700, consists of two main parts, the bottom part and the case. The bottom part contains the push-button set, cradle mechanism including the cradle contact spring assembly, microphone, transmission printed board assembly and a ring unit. The case holds the impulsing printed board assembly and receiver. Two characteristic features of all subcomponents in ERICOFON 700 are low weight and smali volume. Special attention has been paid to the design of the cradle mechanism and the cradle contact spring assembly in order to achieve both low weight and high reliability even if the set is placed on an uneven surface. A one-piece set with all components in the "handset" puts great demands on the mechanical stability of the set. The main construction principle has therefore been to make the set and the mountings for the various parts relatively elastic in relation to each other in order to provide shock absorption. The various units of the set consist of functional blocks that can be tested individually during manufacture and replaced individually during maintenance. The construction of the set is shown in detail in fig. 2. As has already been mentioned, the set consists of two main parts, insert (bottom part) and case. The two parts plug into each other and are held together by three screws. THE INSERT The insert consists of the following parts: • Frame with gasket Push-button dialling mechanism • Cradle mechanism • Recall button (R) ] Transmission unit n Ring unit • Cord Frame with gasket The frame, fig. 3, supports all the structural parts of the set. The frame has been designed with regard to the stringent mechanical strength requirements. It is injection moulded in ABS plastic. The frame is always black irrespective of the colour of the case. In order to protect the surface on which the set is placed, the underside of the frame is provided with a gasket made of injection moulded polyuretane, a material that does not affect or discolour varnished surfaces. Push-button dialling mechanism During the 1960s LM Ericsson developed a push-button dialling mechanism for the internationally recommended V.F. code signalling system. This mechanism, has previously been described in Ericsson Review'. At that time there were several other pushbutton dialling systems in existence, with different "dialling" mechanisms. The production volumes per system were fairly small, which meant that special push-button sets were rather expensive.
121 Fig. 6 Cradle contact spring assembly 1. Frame 2. Contact strip 3. Contact springs 4. Spacer 5. Camshaft 6. Lid 7. Screw During the development of ERICOFON 700 the basic principle was therefore adopted that it should be possible to use the same push-button dialling mechanism for all existing automatic telephone systems. The mechanism works in accordance with the same principles as that for V.F. code signalling. In the impulsing unit push-button signals are converted to the signalling codes of the various automatic telephone systems—V.F. code, d.c. impulsing (instead of a conventional dial) etc. Cradle mechanism The cradle mechanism (fig. 5) is activated at three points, which are placed symmetrically around the pushbutton dialling mechanism, namely by a long key on the front of the set, which activates the two switching bars and also by two buttons in the rear part of the set, which operate one switching bar each. The vertical movement of the cradle buttons is transformed by the switching bars into a torsional movement, which is transferred to the actuating device of the cradle contact spring assembly. Cradle contact spring assembly The requirements regarding low weight for ERICOFON 700, compact structure and a large number of contact functions, led to a new design of the contact spring assembly. The design requirements for this unit were: — small dimensions — low operating force —• large movement margins before and after contact occurrences — contact functions consisting of four changeovers, alternatively four make-before-break contacts with requirements for time sequence between the contact occurrences — a design adapted for mounting on a printed circuit board. The contact spring assembly, fig. 6, contains four separate break contacts and four separate make contacts, which can be connected to form four make-before-break or changeovers. By changing the camshaft, within the limits of eight contact functions, the desired number of closures, breaks or changeovers can be obtained, fig. 7. The construction of the contact spring assembly, with a turning camshaft that works upon the springs, makes possible large movement margins both before and after the contact occurrences without requiring largeractuating force or increasing the stress on the springs. The desired time sequence of the various contact occurrences is obtained through a suitable design of the camshaft, fig. 11. In view of the low voltage of electronic circuits, silver palladium contacts are used.
Page 1: ERICSSON REVIEW 3 1976 GEOSTATIONAR
Page 4 and 5: Geostationary Telecommunications Sa
Page 6 and 7: 112 forever silent. The next launch
Page 8 and 9: 114 Figs. 1—4 Figs. 5—8
Page 10 and 11: 116 Figs. 17—20 Figs. 21—24
Page 12 and 13: Electronic Push-button Telephone Se
Page 16 and 17: Fig. 10 Buzzer unit Fig. 9 Tone rin
Page 18 and 19: Fig. 12 Impulsing unit and ring uni
Page 20 and 21: 126 Fig. 15 Transmission diagram Fi
Page 22 and 23: 128 ed by about 100 kohms. In order
Page 24 and 25: Fig. 20 DC characteristics (speech
Page 26 and 27: 132 use a microphone in which the o
Page 28 and 29: CCM - A Well- tried and Economic Ma
Page 30 and 31: 136 ] Do not allow more staff in th
Page 32 and 33: Ten Years Experience of CCM in the
Page 34 and 35: 140 Table 2 Existing staff requirem
Page 36 and 37: Optimization of Power Supply Equipm
Page 38 and 39: 144 Initial expenditure. This consi
Page 40 and 41: Table 1 Acquisition costs for diffe
Page 42 and 43: 148 Fig. 8 Instead of feeding the p
Page 44 and 45: 150 Fig. 10 Apart from a highly sta
Page 46 and 47: Development, Production and Mainten
Page 48 and 49: 154 combined to meet the needs of e
Page 50 and 51: 156 duction and putting the package
Page 52 and 53: 158 Fig. 5 Working procedure when p
Page 54 and 55: 160 The error message is sent from
Page 56 and 57: Dr. Christian Jacobceus chaired the
Page 58 and 59: 164 Among the reasons that were giv
Page 60: TELEFONAKTIEBOLAGET LM ERICSSON PRI

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