Patent GB-230291-A (GB)
Title: Improvements in impulse sending arrangements for telephone systems
IPC: H04Q3/42
Filed: 1924-04-05
Abstract: 230,291. Siemens Bros. & Co., Ltd., and Humphries, H. E. April 5, 1924. Automatic and semi-automatic exchange systems.-In impulse sending arrangements of the kind in which impulses are sent out while a sending switch hunts for a terminal marked, for example, by a keyboard, the fixed pause necessary after each digit is obtained by causing the switch on its return to normal after sending each digit to hunt for a predetermined number of steps before sending the next digit. The length of the pause may be different in the case of each of the digits of a number. Two arrangements are described using respectively forward and backstroke drive for the sending and sequence switches. The latter arrangement has no controlling relays. Two keyboards are described also, one of which has as many key strips as there are digits, while the other has a single key strip which is connected in succession to digit-recording switches. In the latter arrangement the keyboard grounds all the test terminals in the digit switches but the one corresponding to the key depressed. According to the Provisional Specification the digit switches may be replaced by groups of four relays. Either keyboard can be used with either sender General operation. In the system described, an operator on receiving a call over the line a, b, Fig. 1, plugs into an idle link to a first selector and with the listening key LK thrown presses key CK to associate the cord with the keyboard sending apparatus. If the latter is in its normal position relay CO locks up, connects battery to the top of plug CP and the impulse wire 12 to the ring. Supervisory lamp SL glows until the wanted party replies. Relay N at the keyboard, Fig. 2 or 3, is energized in series with relay CO, locks up and lights the lamp EL. The number is then written down and results in the marking of certain wires in the groups 21 - - 24. The registration of the final digit bridges the wires 15, 16 to start the sender, Fig. 4 or 5. The connection of the marking wire groups 21 - - 24 with the banks of the sending switch C or E is indicated by the numerals 1 - - 0 and the letter n. The starting position for each digit is determined by the connections between the banks of wipers cb, db, Fig. 4, or eb, fb, Fig. 5. Impulses are sent over the wires 12, 13 by a contact of the driving magnet C or by the interrupter 33. When the final digit has been sent the sending apparatus is restored to normal. In a late position of the sequence switch D or F, ground is connected to the wire 27 to energize the opposing winding 2 of relay N and cause its release. In all other positions but normal, wire 26 is grounded to ensure a circuit for the lamp EL when relay N falls back. The relapse of relay N releases relay CO, which connects plug CP to the line ab. Keyboard, Fig. 2. The keys are mechanically latched until another key in the same strip is pressed. A starting contact Z is closed when a units key is pressed. Keyboard, Fig. 3. The depression of any key grounds all the terminals but one in the banks of wipers ma, ha, ta, ua of the digit switches and also energizes the driving magnet of the sequence switch G which, however, does not move its wipers until the key is released. The driving circuit for the digit switches goes over relay J which causes lamp EL to flicker while these are in motion. In the fourth position of the switch G the starting wires 15, 16 are bridged and the lamp SDL lights in series with relay J which extinguishes lamp EL. When relay N falls back, lamp EL lights up until the sender is at normal. When the sender is at normal, a self-interrupting circuit is made for restoring the switch G over its off-normal wiper gc and the wire 11. The digit switches remain in the positions to which they were set. A wrong registration is wiped out by the key WO, which releases relay N by energizing its winding 2 and so causes switch G to be restored. In order to re-energize relay N, the key CK, Fig. 1, must be re-operated. Sender, Fig. 4, using forward drive sending and sequence switches C, D. The bridging of the starting wires 15, 16 moves the switch D to its first position, and slow interrupter 30 is connected to the driving magnet of the sending switch C over dd, q6. Impulses are not sent out, however, until wiper cb reaches the terminal connected to the first terminal in the bank of wiper db. As shown, this happens after two steps, and relay P pulls up over cb, db, q3, q1 P(1), q2, opens the normal bridge across the impulse wires and gives switch D another step. In the second position of switch D, relay Q is no longer short-circuited and pulls up, releasing the driving magnet of switch D. Impulses are now sent out at contact c, until wiper ca reaches the terminal connected, via the keyboard and wiper da of the sequence switch D, to the reverse winding 2 of relay P. Relay P then restores the bridge across the impulse wires and connects the driving magnet of switch C to interrupter 31 which drives it rapidly to normal, whereupon relay Q is released at wiper cx and puts switch C under control of the slow interrupter 30. Switch C now advances to give a fixed pause, until wiper cb reaches the terminal connected to the 2nd terminal of the bank of wiper db, after which relays P and Q pull up and the next digit is sent as before. After the final digit the switch C returns to normal as before, but relay Q remains locked over wiper dc while the switch D is being restored. Switch D is moved as before to its 5th position at the beginning of the units digit, and when relay P falls back at the end of the digit the driving magnet is connected to interrupter 30 over dx, p4. The contact d maintains the circuit while the wiper dx is between terminals. In the 7th position of switch D, wiper df grounds wire 27 to release relay N, Fig. 2 or 3, with results described above. Sender, Fig. 5, using back-stroke drive for the sending and sequence switches. E. F. The interrupters 32, 33 have a make-to-break ratio of 1: 2, and operate at the same speed, but 33 does not make until 32 is in the middle of its " make " period. The bridging of wires 15, 16 connects interrupter 32 to the driving magnet of the sequence switch F over wiper fc and at the first " break " period of 32 the switch takes a step, and connects the driving magnet of switch E to the interrupter 32. Switch E is thus stepped to the starting position for the first digit as determined by the connection between the banks of wipers eb, fb. In this position, interrupter 32 is connected over these wipers to the driving magnet of switch. F so that at the next " break " of 32, the wiper fd removes the normal bridge from the impulse wires and impulses are sent from 33 slightly after the stepping impulses of 32. Switch F remains in its 2nd position until the first break after wiper ec of switch E reaches the terminal connected via the keyboard and wiper fc to the driving magnet of switch F. Wiper fd then restores the bridge across the impulse wires and wiper fa completes a self-interrupting circuit for driving the sending switch to normal. In the normal position of switch E a circuit is made over f, fb for the driving magnet of switch F which takes a step by self-interruption and connects the sending switch to 32 for the " fixed pause " period, after which the switch F takes another step and the sending of the second digit begins. When all the digits have been sent, both switches are restored by self-interruption, wiper fe connecting ground to wire 27 in its 13th position to release relay N, Fig. 2 or 3.