Patent GB-158556-A (GB)
Title: Improvements in electromagnetic wave signalling systems
IPC: H04L27/04
Filed: 1921-01-22
Abstract: 158,556. Regnauld de Bellescize, H. J. J. M. de. Jan. 22, 1920, [Convention date]. Type-printing telegraphs; synchronous movements.-Comprises adaptations of the Baudot system of type-printing telegraphy to wireless signalling systems. Secrecy may be effected by arranging that the impulses which build up a letter are sent out from distributor segments chosen in a predetermined irregular fashion. Means are provided to enable a letter or letters to be set up whilst the distributor is sending out the impulses corresponding to the previous letter. The distributors at the two stations may be synchronized by special impulses, or by the signalling impulses alone. Figs. 1 and 1<a> show one form of the transmitter and receiver. The distributor D1 at the transmitter is divided into a number of zones I, II, &c. each including five segments, and two segments 21, 22 for synchronizing. The segments of each zone are connected to a group of keys M1 - - M5, each group of keys serving for sending one message, thus allowing, in the example shown, four messages to be sent simultaneously. Each key when depressed prepares the circuit of a relay H1, which is energized when the rotary arm L1 reaches the corresponding segment. When inoperative, the keys prepare the circuit of a relay H2. These relays as shown control a short-circuiting switch N by which the frequency of the carrier waves is varied. Instead of using two wave frequencies, two note frequencies may be employed. At the receiving station the two kinds of signals are separated by tuned circuits R1, R2 and act oppositely on a switch J. A similar distributor D2 has its segments connected to relays E1 - - E5 with the result that depression of any key at the transmitter energizes the corresponding relay at the receiver. These relays energized in various combinations select in known manner the letter required on the type wheel. In the arrangement shown, a number of arms C1, C2, &c. are set in turn in positions corresponding to all the code combinations, by means of cam discs on the distributor shaft. At the moment when the setting of the arms C, .. is identical with that of the armatures K1 .., the printing magnet F is energized and presses the tape against the type wheel, which rotates with the distributor. In order to keep the distributors in synchronism, the two contacts 21, 22 at the transmitter are arranged to send out the working wave and the inoperative wave in succession at the end of each revolution. Of the corresponding contacts 21', 22' at the receiver, the latter is connected to a speed-reducing magnet B. The brush L2 at the receiver is arranged to rotate slightly faster than the transmitter brush L1, and if the brush L2 reaches the contact 22<1> whilst the brush L1 is still on the contact 21, the magnet B is energized to reduce the speed of the brush L2. In order to prevent these synchronism signals being utilized for listening in, the arrangement shown in Fig. 3 may be substituted, in which the signal impulses are used for maintaining synchronism. The receiver brush is connected to a rotary commutator O having twice as many segments as the distributors. Alternate segments are connected respectively to slip rings engaged by brushes Q1, Q2. A pivoted stationary brush V is arranged to be brought into engagement with the segments as each impulse is received. A circuit is thus made from battery P4 through one or other of the opposed coils Y1, Y2, according as the receiver brush L2 is in advance of, or behind, the transmitter brush L,. The coils Y1, Y, form additional field windings to the motor X by which the brush L2 is driven, and their energization adjusts the speed of the motor to bring the brushes into synchronism. Large condensers I are shunted across the coils Y1, Y2. Fig. 2 shows a transmitting arrangement in which secrecy is secured by irregularity in the order in which the impulses constituting a single letter are sent out. As shown therein, the armatures K1 - - K5 controlled by the keys M1 - - M5 are connected to the segments numbered respectively 1, 13, 5, 9, 17. Any 'other predetermined sequence of numbers may be chosen, and may be brought into operation by shifting the arms X. Other groups of five numbers may be used for the simultaneous transmission of other messages. In order that one letter may be set up by the keys M1 - - M5 whilst the previous letter is being sent in the form of impulses to the relays H1, H2, the keys operate levers T which are held up by magnets U1 - - U5 so long as the brush L1 is passing over contacts 3-20. During the setting of the keys M and levers T the impulse-sending armatures K are in the position corresponding to the previous letter, the springs R1, R2 allowing sufficient freedom for this. When the previous letter has been completely sent, the magnets W are all de-energized owing to the brush L1 reaching a gap in the ring connected to these magnets. The armatures K then take up their new positions corresponding to the next letter, under the influence of the springs R1, R2, and the magnets W, are again energized to maintain them in their new position. Immediately afterwards, the magnets U1 - - U5 are deenergized to allow the levers T to fall back, so as to be ready for setting according to the next letter. As the brush L1 passes the third segment a warning is given to inform the operator that the next letter may be set up. At the receiving station the mechanism is the same as at the transmitter except that the keys M1 - - M5 are replaced by magnets each connected in series with a " secrecy " arm X, the corresponding distributor segment, a battery, and the relay switch J, see Fig. 1<a>. The setting of the elements K at the receiving station selects the letter to be printed in the manner described above for Fig. 1<a>. The Specification as open to inspection under Sect. 91 (3) (a) comprises also a modified receiving-arrangement shown in Fig. 4 (Cancelled), in which five magnets A, B, C, D, E at the receiving-station are arranged to move their armatures through distances proportional to 1, 2, 4. 8, and 16. Each armature carries a. pulley, and a cord looped round the pulleys, as shown, is fixed at one end and attached to the type-wheel H at the other. Energization of the magnets in various combinations gives 31 positions of the type-wheel. This subject-matter does not appear in the Specification as accepted.