GB952256A - Improvements in character generator devices - Google Patents

Abstract

952,256. Semi-conductor devices. CSF-COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. Feb. 27, 1962 [March 2, 1961], No. 7708/62. Heading H1K. [Also in Divisions G4, H3 and H4] In an arrangement for tracing Alpha- Numeric characters on the screen of a cathoderay tube three voltage-time function generators x 1 , y 1 , z 1 (Fig. 2) are provided for each character and connected respectively to the horizontal deflection plates, the vertical deflection plates and the intensity control electrode of the tube. Fig. 1 shows the sequence of events in tracing the letter " A " by means of a continuous line under the control of voltage-time functions x(t), y(t) and z(t). The initial point P o , the trace between P o and a being blanked by the function z(t), is determined by positioning voltages X, Y, applied either to auxiliary deflection plates or combined with the function voltages x(t), y(t). In practice a plurality of function generators is employed and grouped as shown in Fig. 2 which is concerned with tracing characters corresponding to the output signals of a computer 1 such signals being fed to a decoder 2 together with synchronizing signals from a source 5. The various outputs of the decoder on lines C 1 . . . C n (which may also supply on lines 3, 4, the positioning voltages X, Y referred to above) comprising square wave pulses are supplied to different groups of three function generators, each group producing the respective function x, y, z appropriate to a particular character in response to a pulse input. Fig. 3 shows one form the function generators may have and comprises a semi-conductor bar 11 provided with a collector electrode C and a plurality of equidistant emitter electrodes e 1 . . . e n each connected to a common input line 12 via R.C. networks R 1 . . . R n . A source 17 supplies polarizing potential and a further adjustable voltage source 14 provides a longitudinal drift field in the bar which directs the carriers injected by the emitters towards the collector. In operation an input pulse applied to line 12 (e.g. from the decoder 2 of Fig. 2) produces on the output line 13 a voltage time-function the duration of which may be up to 15 Á.secs. and the shape of which is determined by the networks R 1 . . . R n . For a given value of voltage from source 14 the phase of the output (time-function) voltage with respect to the input pulse depends only on the distance between the collector C and the nearest emitter (in this case e 1 ) and the duration of the output voltage depends on the spacing between the extreme emitters e n and e 1 . To obtain more accurate tracing each function generator may comprise two units of the kind shown in Fig. 3, the outputs being connected in parallel and the input of one connected to the input of the other via a delay line. The generators may be modified to provide for discontinuous plotting, e.g. by dotted lines. Instead of employing a semi-conductor the function generators may comprise a conventional delay line having either a plurality of inputs connected to a general input via passive networks and a common output, or, a plurality of outputs connected to a general output via passive networks and a common input. French Specification 1,290,298 is referred to.