Patent GB-312209-A (GB)
Title: Improvements relating to cable telegraphy
Filed: 1928-02-21
Abstract: 312,209. Beatty, W. E., (Bell Telephone Laboratories, Inc.). Feb. 21, 1928. Restoring imperfect signals; distributor systems.-Relates to means of the kind described for instance in Specification 296,131, for restoring in telegraphic reception the short impulses which have been lost through distortion in the line. According to the invention this result is achieved by means of two vibrating relays which mutually actuate one another, and a single pair of distributor rings of which one is solid and one segmented. In the absence of incoming effective line signals the main vibrating relay MVR and auxiliary vibrating relay AVR of a telegraph printer co-operate with the vibrator ring VR to rock the armature 18 to the right or left once per signal period, the segments 1 feeding the relay AVR while the segments 2 feed the relay MVR. A pair of segments 1, 2 corresponds to one signal period. In the position shown in Fig. 1 negative current passes through the brush 32, a segment 1, and the upper winding 5 of the relay AVR, so that the tongue 13 is set to the left. When therefore the brush 32 reaches the next contact 2, negative current passes through the vibrating winding VW of the relay MVR from right to left. The tongue 18 of that relay is thus set to the left so that the next impulse from a segment 1 passes through the lower winding 6 of the relay AVR, setting the tongue 13 to the right; thus the next impulse through the winding VW passes from left to right and the tongue 18 is therefore rocked to the right again. The movements of the tongue 16 thus represent a sequence, of signal impulses of opposite polarity, and this cycle of movement continues so long as such a sequence is actually being received over the line L1 and amplifier A, since the isolated impulses are too much weakened by distortion to affect the relay MVR. When, however, two or more successive impulses of the same polarity are received, the current in the line winding LW rises to a sufficient strength to overpower the effect of the local currents and the cycle of vibrations of the tongues 13, 18 is suspended for the required number of signal periods. The movements of the tongue 18 thus correspond to the signals actually passing over the line. Resistances 3, 4 are provided to protect the contacts, and resistances 14, 15 to improve the operating characteristics of the relay AVR. The resistances 7, 8 are of such value that the currents in the winding VW are of the right strength in relation to the currents in the winding LW. Type-printing telegraphs.-The printer magnets 22 - - 26 are connected in succession to battery negative through the brush 33 and printer rings PR. Their opposite terminals are permanently connected to the contact 16, so that they are energized or not according as the tongue 18 is to the right or left, i.e., in accordance with the polarity of the line signals. Multiplex telegraphs; synchronous movements. -The printing magnets 22 - - 26 belong to one channel and the magnets 22<1> - - 25<1> to the next channel. In order to ensure that synchronizing signals shall be sent in the absence of messages, the polarity of the impulses is reversed in meaning in alternate channels. Correspondingly, the magnets 22<1> - - are connected to the contact 17 instead of the contact 16, and the connections of the remaining channels (not shown) alternate in a similar way. Repeating systems using contact-making relays. -Signals may be repeated, in accordance with the movements of the tongue 18, by means of an auxiliary repeating relay ARR, Fig. 3, having two opposed windings which are connected on one side to battery positive and on their other sides to the contacts 16, 17 respectively. The tongue 38 is thus rocked in conformity with the tongue 18, and repeats the signals to the line L2.