Patent GB-477320-A (GB)
Title: Improvements in or relating to selective receivers for marine distress signals
IPC: H04L15/26
Filed: 1936-03-18
Abstract: 477,320. Electric signalling systems. IVANOV, D., WITTMANN, B., and IVANOV, A. March 18, 1936, No. 8091. [Class 40 (i)] In a selector which is responsive only to a code of dashes and pauses of predetermined duration, a step - by - step selector is driven under the control of the signals by a pair of interacting relays, one of which is timed in its operation. As shown in Fig. 1, the selector comprises three banks of contacts having brushes driven stepby-step by a stepping magnet 13 which is under the control of relays 14, 6, the latter of which has a timed release. Normally, relay 6 is operated over contact 4 of the receiving relay 2 and the normal contact 7 of the bank 8 of the switch. The selector is adapted to respond to a signal consisting of three dashes each having a tolerance of 3À5 to 4À5 seconds separated by pauses of 0À5 to 1À5 seconds. The timed relay 6 has a relapse period of 0À5 seconds. On the receipt of a signal of length greater than 0À5 second, the relay 6 is released ard the contacts 9, 10 close and operate relay 14 and stepping magnet 13. Relay 14 releases the magnet 13 at contacts 15, 16 to cause the switch to step and also reoperates relay 6 which again releases 14. Relays 6, 14 continue to interact over circuits including bank contacts 17, 18 at a period of 0À5 second and the selector steps at the same rate. If the relay 2 is released during the toleration period of the first dash, a circuit is completed over contacts 21, 22, 26 and automatic contact 25 of the stepping magnet 13 to provide a self stepping circuit for the switch which moves rapidly to the position which corresponds to the first pause measuring position. The relay 14 also is operated to pull up relay 6 and thereby ensure that a full release period is given to the relay preparatory to measuring the pause. At the end of a correct dash, contact 4 drops back and a time check of the pause is initiated at contact 99. During the pause the switch is stepped under the control of the relays 6, 14 in the manner previously described, automatic stepping to a position corresponding to the commencement of the second dash taking place over contacts 29, 30 in the event that the contact 4 is again operated during the toleration period of the pause. Similar checking operations occur during the reception of the second and third dashes and the second pause until when the contact 4 drops back at the end of the third dash, a relay 35 is operated over contacts 33 or 34 to switch in the alarm 92. If the first dash is short, relay 20 is pulled up over group 55 ... 60 and the self-drive circuit of the magnet 13 is completed over bank 17 to restore the selector to normal. Similar operations occur in the event that the second and third dashes are short. The relay 20 also is operated over contacts 51, 53 if the pauses are short. Long dashes cause restoration over contacts 65, 53, 54, the restoration in the case of a first long dash being delayed until the termination of dash owing to the simultaneous operation of relay 14 and the consequent opening of the restoration circuit at contact 66. Relay 62 is provided to pull up relay 6 in the event of a short pause and the consequent restoration of the switch in order to recondition the apparatus for correct response to the next incoming dash. In a modification, a selector with fewer contacts is arranged to rotate twice to perform a complete check of the incoming signal.