Patent GB-1175189-A (GB)
Title: Improvements in or relating to Circuit Arrangements Including a Cathode-Ray Tube.
IPC: H01J29/72
Filed: 1966-12-14
Abstract: 1,175,189. Cathode - ray tube operating circuits. PHILLIPS ELECTRONIC AND ASSOCIATED INDUSTRIES Ltd. 14 Dec., 1966 [17 Dec., 1969], No. 55934/66. Heading H4T. In a cathode-ray tube display arrangement in which signals from a source 7 (Fig. 1) produce vertical deflection of a horizontal timebase the vertical deflection means comprises a first part 3a and a second part 3b (e.g. a deflection coil) the signals from source 7 being combined with an auxiliary signal from source 8 and supplied to plates 3a whilst the second deflection means 3b is supplied with a portion of the auxiliary signal via adjusting means 10. This arrangement allows the extend of the deflection on screen 5 to be increased over that otherwise limited by the spacing of plates 3a. Thus, referring to Fig. 2, if the deflection signal from source 7 varying between + Vm and - Vm produces, when applied alone to plates 3a, a trace on screen 5 limited by the dotted lines 15, 16, the addition of an auxiliary signal - V (to plates 3a only) would allow the deflection voltage to be increased to Vm + V. However as the deflection voltage now varies between + (Vm + V) and - (Vm + V) the portion between- Vm + V and- (Vm - V) will be cut-off at line 16 (b, Fig. 2). To overcome this a portion of the auxiliary signal selected by means 10 is applied to the deflection means 3b to bring the deflection due to the signal + Vm to the line 15 so the deflection due to level +(Vm + V) now exceeds this limit of line 15 as shown at c, Fig. 2. Thus the portion between - Vm + V and + (Vm + V) is displayed and by reversing the sign of the voltage V and also that of the portion supplied by means 10 to the deflection means 3b the portion between +Vm - V and - (Vm + V) may be displayed, as shown at d, Fig. 2. This is achieved by using for the auxiliary voltage a square wave having an amplitude (+ V, - V) which may be derived by limiting and amplying (if necessary), the deflection signal from source 7 or it may be derived from the horizontal time base 6 to the frequency of which it should be integrally related. When V = Vm the traces do not overlap, i.e. the portion between + Vm - V and - Vm + V is not reproduced, and a signal of amplitude up to twice that corresponding to the maximum deflection of the tube may be reproduced. When V is greater than Vm a blank region appears between the traces. When V = 2Vm a widening factor of 3 may be produced by utilizing steplike auxiliary signal (+ V, O, - V) and a widening factor of 4 by an auxiliary signal having step values (+ 3Vm, + Vm, -Vm, SVm). Instead of having a step-like form the auxiliary signal may have a sawtooth, tri. angular or sinusoidal form. When the trace produced by the deflection signal involves two portions "written" with different tracing velocities uniformity of trace intensity is achieved by utilizing the auxiliary signal to cause the portion "written" at the higher velocity to be retraced a plurality of times during one tracing of the portion(s) "written" at the higher velocity. (Fig. 3, not shown).