Patent GB-301557-A (GB)
Title: Improvements in apparatus for the electrical transmission of data over comparativelylong distances
Filed: 1927-09-06
Abstract: 301,557. Barr &. Stroud, Ltd., and French, J. W. Sept. 6, 1927. Order apparatus. - In an electric signalling system of the " follow the pointer " type, a pointer having a limited angular movement is adapted to follow or be followed by a set of pointers rotatable about the axis of the single pointer and disposed angularly about the axis at angles corresponding to the angular movement of the single pointer. The arrangement is such that each complete angular movement of the single pointer when, say, it acts as a leader pointer is associated with a different follower pointer during one complete rotation of the follower pointer. As shown in Fig. 1, in which the leader and follower pointers are shown mounted on different axes for convenience of illustration, a, set of leader pointers 3, 14, 29, 30 at the transmitting station is driven by a step-by-step motor controlled by a commutator switch 2. Any one of the pointers may be set to the desired indication, and the pointer 6 of a galvanometer 7 may be set to correspond by adjusting the contact arm 5 of a potentiometer resistance. 34. A galvanometer 9 at the receiving station is connected in series with the instrument 7, and the movement of its pointer 8 is followed by a set of pointers 12, 24, 31, 32 controlled by a step.-by-step motor and a commutator switch 10. When, say, the pointer 3 passes off the scale the pointer 6 is returned to its zero position in readiness for co-operation with the succeeding leader pointer 14. Similarly at the receiving station the pointer 24 co-operates with pointer 8 after restoration to zero simultaneously with the pointer 6. Upon the appearance of each successive pointer of the instruments Y-mechanisms 15, 25 operate the commutators 16, 26 of coarse indicators 18, 28. The contact arm 19 of the potentiometer 35 controls the follower and leader instruments 21, 23 associated with the instruments 18, 28. Each indicator 18, 28 may be provided with a plurality of angularly-disposed pointers in order that a larger range of indications may be obtained. In order to avoid the frequent return of the pointer 6 to zero when a leader pointer, say 3, oscillates about the extremity of its scale, the scale may be extended for a few divisions. Supplementary scales may also be provided in the coarse instruments. Instead of employing two commutators 10, 26, a single commutator controlling a step-by-step motor which drives both fine and coarse pointers through suitable gearing may be employed. In order that the pointers of the galvanometers may be returned to zero rapidly, each contact arm 5, 19 is adapted to be returned under spring control upon manual release. The handle 5, Fig. 6, controls the contact arm 45 of the potentiometer resistance 34 through differential gearing 46, 47, 48. The wheel 48 is normally held stationary by a lever 38 and toothed wheel 50, and when the handle 5 is operated, the arm 45 is rotated and a control spring 51 is wound. Upon release of the lever 38 the arm 45 is returned by the spring to its zero position, and simultaneously the galvanometer pointers are restored. Specification 301,127 is referred to.