Patent GB-1404460-A (GB)
Title: Device for transmitting cursive script or drawi'g over a  telephone
IPC: G06F3/033
Filed: 1972-11-28
Abstract: 1404460 Transmitting script or drawings; recording apparatus STANDARD TELEPHONES & CABLES Ltd 28 Nov 1972 54880/72 Headings G1J and G1N [Also in Divisions G3 H1 and H4] Apparatus for transmitting cursive script or drawing over a public telephone network comprises a position transducer 6, Fig. 4, which combined with resistors 26, 27 and a power supply 20 provides voltages representing X and Y coordinates; these voltages are converted to frequencies at 29, 30 for transmission over the telephone network by a direct electrical connection or by acoustic connection. The frequencies are received by the apparatus of Fig. 5 which operates two pointers whose intersection corresponds to the position of a writing pen on the transmitter position transducer. The intersection traces out the path of the pen as described later. The position transducer is shown in Fig. 2, and comprises two sheets of transparent plastics sealed together at the edges. The sheets are separated slightly by gas trapped between them, so that X and Y conductors on the facing surfaces of the two sheets are usually spaced apart. When pressure is applied to the sheets by a pen, one of the X conductors 17 contacts one of the Y conductors, so that one of the terminals 19 is directly connected to one of the terminals 18. As seen in Fig. 4, each conductor is connected at one end to its adjacent conductor by a resistor 26 or 27, and is connected at its other end, via isolating diodes 24 or 25 to chopping switch 21 and power supply 20. A second chopper 28, in synchronism with the first, grounds the resistor chains 26, 27 alternately. With the pen applied to the transducer 6, the chopper 21 passes current to the X and Y conductors alternately, and the values of resistors 26, 27 is arranged so that the current value is a unique indication of which pair of X and Y conductors are in contact. The current also passes through resistors 22, 23, and the voltage across them is converted to a frequency at 29, 30 for transmission in two frequency bands. The receiving apparatus of Fig. 5 separates the bands and drives pointers 39, 40. These are shown as pivoted, but linearly moving devices may be used. The two pointers are shown in more detail in Fig. 6, the lower one 39 being bar-like while the upper one carries rods 41 which may be displaced upwardly as at 41a but which are normally held down by a spring 43 engaging slots 42. The pointer 39 is vibrated up and down, e.g. by a loud-speaker diaphragm (not shown) moving at 100 Hz, so as to drive one of the rods 41 up and down. The rod strikes a pressure sensitive sheet (not shown) to indicate the position of the pointer intersection. As the pen on the transmitter moves, rods 41 trace out its path. The sheet may use a waxy paper which adheres to a glass sheet when struck by the rod, such an arrangement being erasable. The equipment described may be built into a telephone hand-set, as in Fig. 1. The transmitting transducer 6 overlies a sheet of pressure sensitive paper 7 on which a record of the transmitted information appears. To receive information, transducer 6 is lifted up, paper 7 is removed, and the pressure sensitive paper 10 of the receiver may then be seen. Bulbs 13 provide illumination for reading. The equipment shown may be retracted into the telephone set body 2 when not in use. When it is pulled out for use switches may operate to cut out the telephone voice transducer to prevent crosstalk with the transmitted script or drawing. If the pressure sensitive sheets are semitransparent, the transmitted and received information may be superimposed, in effect giving a two way system.