Patent GB-407771-A (GB)
Title: Improvements in or relating to telephone instruments employing key or like switches
IPC: H04M1/52
Filed: 1932-11-03
Abstract: 407,771. Keyboard switches. ERICSSON TELEPHONES, Ltd., 67, Kingsway, London, NEWELL, G. R., and HOLLIS, F., Ericsson Telephone Works, Beeston, Notting- ham. Nov. 3, 1932, No. 30951. [Class 38 (v).] In a telephone instrument incorporating interlocked keys or other switching members operating electrical contact springs, for use particularly in an intercommunication system, the keys and interlocking arrangements form a unitary structure independent of the receiver support and readily detachable from the spring assembly. The springs are carried by the base of the instrument which also incorporates the remainder of the sub-station equipment. When the key assembly has been inserted in position, the apparatus is enclosed by a cover which supports a cradle switch. The instrument described is for use in the inter-communication system described in Specification 383,747, [Group XXXIX], and reference letters, and numerals below 30, are those used for corresponding parts in the prior Specification. The base plate 89, Fig. 3, carries buzzer Bz, relays E, F, induction coil 100, cradle switch springs CS, springs CK controlled by all intercommunication keys, and a number of key operated spring sets of which three, a, band 110, are shown in Fig. 3. The key operated sets may comprise two rows, as shown in side view in Fig. 7, carried by supports 88. The key assembly is carried by a plate 93 detachably secured to the supports 88 by screws 98, Fig. 2, and when two rows of keys are used their stems pass down between the two rows of spring sets as shown. The cradle switch member 37, Figs. 4 and 6, is controlled by a pair of plungers 36, Fig. 2, in the cover on which the hand-set normally rests, and an upstanding arm 41 on member 37 normally holds key locking members 43, 45 in the inoperative (right hand) position by engaging downward projections 42, 44 on the locking members. The keys comprise local connection keys LK and exchange line keys EK. The local keys have stems shaped as in Fig. 8 slidable in guides in the frame against the action of springs 51. Bevelled projections 55 on the stems are adapted to pass beneath and be held by projections 62 in apertures 49 in locking member 45 when this member has been released by the cradle switch member 37. The member 45 is urged towards the left by a spring 48. The stem 56 of an exchange key EK is of similar form but its upper end is turned over and shaped as at 57, Figs. 4 and 6, to ride in a slot 60 of an auxiliary stem 59 shown separately in Fig. 9, so that when an exchange key is pressed, its main stem is locked as in the case of a local key but the auxiliary stem is held down by the engagement of a step 61 thereon under a projection 63 of the locking member 43. When a local key is pressed it moves locking member 45 to the right thereby releasing any other local key that may have been pressed subsequent to removal of the hand set and also releasing the main stem of an exchange key that may have been pressed. This allows a local consultation during an exchange call since although the release of the main stem of EK disconnects the exchange line, the auxiliary stem 59 remains depressed and keeps spring set a, Fig. 3, operated to hold the connection. The exchange key may be manually held down during a local consultation and exchange keys may be interlocked so that only one may be pressed at a time. If two or more keys are pressed simultaneously both or all are held depressed to provide conference facilities, or, a conference key CB may be pressed so that the local keys arc held even if depressed successively. Depression of CB which is connected to a member 64 moves to the left a carriage 71 by virtue of an inclined slot and pin connection 69, 70. The key CB is latched by a member 80 which is moved to the left by a spring 81. The carriage 71 has pawls 76 (one for each key-stem) pivoted at their upper ends and abutting against the sides of steps 78 in the key-stems when the carriage is moved to the left. If, now, the keys are pressed successively, they are held by the pawls 76 engaging over the top of the steps 78. The conference key may also control the exchange keys in a similar manner. It may also be released by pressing an exchange key. When the hand set is removed from the cradle, an insulating stud 90, Fig. 6, on the upstanding part 41 of the switch member 37 and which normally stresses the spring set CS, Fig. 2, is removed therefrom, and a similar stud 92 on a pivoted member 91 engaging the forward end of the projection 44 on locking member 45 permits spring set CK to become unstressed. A line is called by pressing a key say LK3, Fig. 7, to its fullest extent so that the upper end of projection 84, Fig. 8, on its stem operates the key spring set sufficiently to close springs 109, 110. At the same time, locking bar 45 is moved sufficiently far to the right to operate member 91 and move the spring set CK so that springs 12, 13, Fig. 3, are closed. This completes the calling circuit and when the key is released it moves upwards somewhat until held by projection 62, Fig. 4, in the partially depressed speaking position. When the telephone instrument is replaced, member 37 releases all operated keys by drawing the locking members 43, 45 to the right. The conference key, if operated, is released by interconnection between its locking member 80 and member 43.