Patent GB-185429-A (GB)
Title: Improvements in devices for indicating and recording the duration of trunk line telephone calls
IPC: H04M3/12
Filed: 1921-08-31
Abstract: 185,429. Allmõnna Telefonaktiebolaget, L. M. Ericsson. May 20, 1921, [Convention date]. Short time movements. - In a device for indicating and recording the duration of trunk calls, two pointers, one indicating parts of a period and the other indicating full periods, are formed with points or edges and are moved along a rigid graduated rule, the divisions of which are also formed as points or edges. To record the duration of a call a card is pressed against both the rule and the pointers, thereby producing on it an impression of the graduated rule showing the relative positions of the two pointers. Construction of indicator. The indicator mechanism is mounted in a frame for attachment to the switch-board, and is controlled by a shaft 5, Fig. 4, which is rotated against a spring 16, Fig. 3, by a ratchet 4 and a pawl 3 pivoted to the armature 2 of a magnet 1 responding to the controlling impulses. A holding pawl 6 is also provided which is released by a projection 10 on the armature 9 of a restoring magnet 8, Fig. 3. The shaft 5 is coupled by a catch 17 to an extension 50 on which is mounted a pinion 18 meshing with a sliding rack 19 which is guided by a rib 20 and carries a punch-pin 22 and a visual partperiod pointer 21 associated with a scale 26 visible through a window 51. A fixed bar 23 is mounted in front of the rack 19 and is formed with division pins 24, which, when a card is inserted through the opening 49 and pressed up by the armature 48 of the stamping magnet 47, produce an impression of the scale. In front of the bar 23 is another bar 25 slidably mounted and furnished with a visual full-period pointer 27 and a punch pin 28. This bar 25 is provided with ratchet teeth 29, Fig. 5, the pitch of which corresponds to the distance between two of the points 24 on the scale bar 23, and which are adapted to co-operate with a stepping pawl 30 and a retaining pawl 31. The pawl 30 is formed with an arm 34, Figs. 2 and 5, which passes through a slot 33 in the frame and is engaged by a stop on the bar 19 when the latter has almost reached the end of its travel. The pawl 30 is thereby rotated in the slot 33 and engages a tooth 29 of the bar 25, which then moves with the bar 19 for the remainder of its movement, the pawl 30 sliding in the slot 33. The retaining pawl 31 is formed with an arm 37 which is engaged by a lever 53, Fig. 2, when the bar 25 is to be restored. The lever 53 is pivoted to rotate in a vertical plane about a point 54, and is also capable of being rotated in a horizontal plane by a projection 52 of the armature 9 of the restoring magnet 8. Normally the energization of the magnet 8 does not cause the release of the pawl 31 and the return of the fullperiod bar 25, as the lever 53 swings clear of the arm 37, but when the call has been completed and the stamping-magnet 47 is energized, the relapse of the armature 48 causes a projection 55 thereon to engage a pawl 54 attached to the lever 53, which is now moved opposite to the arm 37 so that when the restoring magnet 8 is subsequently energized the pawl 31 is released and the bar 25 is restored by the spring 46, Fig. 5. The lever 53 is also adapted to be brought into this operative position when the maximum reading of the device is arrived at, that is, when the full-period bar 25 has reached the end of its travel. In this position a projection 44, Fig. 5, on the bar 25 moves the lever 53 opposite the end of the arm 37, so that when the restoring magnet 8 is energized both bars 19, 25 are released. Operation, Fig. 7. Two starting keys 56, 57 for " forced " and ordinary calls respectively are provided on the front of the device, and the depression of either key completes a circuit for the stepping-magnet 1 over the lead a over which impulses are transmitted from suitable mechanism at a uniform rate, say 10 per minute. The shafts 5, 50 are thus rotated by the ratchet 4, and the part-period bar 19 with its pointer and pin is moved towards the right. After the ratchet 4 has moved two steps, a pin 13 mounted on it closes a pair of contacts 15, and a circuit is completed, over the normally-closed contacts 81 and the contacts 56<b> or 57b of the depressed starting-key, for the " forced " or ordinary call meter 62 or 63, which registers a period. Just before the ratchet 4 completes its twenty-fifth step, a stop on the bar 19 strikes the arm 34 of the pawl 30, which engages the first tooth of the full-period bar 25, causing this bar to travel with the part-period bar 19 for the remaining five steps. Two steps before the end of the first period, a pin 12 on the ratchet 4 closes the contacts 14, thereby completing the circuit of a lamp 59 or 60, which is mounted on the front of the device and warns the operator that 3 minutes has almost expired. At the thirteenth and last step, a pin 39 on the bar 19 closes contact 41 and a circuit is completed over the off-normal contacts 40 for a restoring relay 64, which locks up and completes a circuit for the release magnet 8. The magnet 8 releases the holding pawl 6, and the part-period bar 19 is restored to normal, the full-period bar 25, however, being held by the retaining pawl 31. During this restoring operation the contacts 81 are opened to prevent the operation of the meters 62, 63 and the lamps 59, 60 by the closure of the contacts 14, 15 on the return of the ratchet 4. When the bar 19 reaches its normal position, the separation of the contacts 40 de-energizes the restoring relay 64 and the release magnet 8, and on the arrival of the thirty-first impulse the cycle is begun again. Just before the bar 19 reaches its twenty-fifth step it is coupled by the pawl 30 to the bar 25, which is then moved a second full-period step. This operation continues as long as the call proceeds, the bar 25 being advanced a step and the bar 19 being restored at the end of each threeminute period. When the conversation is finished, the operator inserts a card in the slot 49 and depresses a third key 58 on the face of the instrument, thereby energizing the call. recording meter 66 and the stamping-magnet 47 in parallel over the contacts 81, and producing on the card a record of the scale and the positions of the pins 22, 28. The key 58 is then released and the relapse of the armature 48 closes the contacts 69, energizing the restoring relay 64 which in turn energizes the magnet 8 and brings about the restoration of the device as described in the previous paragraph. Means are provided whereby the device is automatically released and the operator signalled each time the maximum time, i.e. 18 minutes, is registered. When the bar 19 near the end of the sixth period aproaches its final position, the bar 25 also approaches the end of its travel, and the contacts 43 are closed by an abutment 42, Fig. 5, on the bar 25, in addition to closure of the contacts 41 by the bar 19. Contacts 43 close circuits for a warning lamp 61 and a relay 65, which locks up over its contacts 65<a> and the normally closed contacts 58<a> of the restoring key 58, the lamp 61 then being energized in a parallel circuit. The energization of the magnet 8, following the movement of the lever 53 by the projection 44 on the bar 25, releases the device as previously described.