GB652154A - Improvements in or relating to telegraph translating circuits - Google Patents

Abstract

652,154. Code telegraphy. RADIO CORPORATION OF AMERICA. Sept. 19, 1946, No. 28157. Convention date, Sept. 26, 1945. [Class 40 (iii)] [Also in Group XL (c)] Apparatus responsive to pulse energy which shifts from one value representing a mark to a second value representing a space and which terminates at one of said valves comprises a tripping circuit coupled to an output circuit and controlled by said pulses and having two positions of stability, one of which represents a mark and the other a space, so that the tripping circuit comes to rest in one position determined by the value at which the pulse energy terminates, also includes means for restoring the tripping circuit to said one position of rest in case it has been tripped therefrom by energy due to static or other disturbance. The arrangement is preferably used in a system in which marks and spaces are transmitted by different frequencies which are fed to a limiter, discriminator and detector to derive bidirectional current which reverses the output polarity as the transmitted current shifts from the mark frequency to the space frequency and vice versa. The positive and negative impulses applied at 102 to a valve 104 are taken from a cathode resistor 108 and fed to the first valve 110 of a triggering pair and to a valve 150 which is made normally conducting by means of slight positive grid bias derived from a resistance 154 connected to a potential divider 155, 156. The valve 110 conducts on a mark and the valve 114 on a space, the output being taken from the plate circuit of either of the valves 110, 114, and from 114 as shown. If, at the termination of signal keying, the valve 114 has been left conducting due to a disturbance, since valve 150 gradually returns to its conductive state, the flow of current in this valve and through the resistance 123 will reduce the potential on the grid of valve 114 which cuts off and makes the valve 110 conductive. During the initial spacing pulse, valve 150 is made non-conducting and this applies a slight positive potential to the grid of the valve 114 and aids the triggering to be effected by the application of the normal spacing (negative) voltage to the grid of the valve 110. During keying, the mark impulses apply a slight positive potential to the grid of the valve 150, which conducts to a small extent and by reducing to some extent the positive voltage on the grid of the valve 114 aids the triggering of the valve 110 by the mark impulse. The cathode resistance 111 is variable so that in the case of input waves with sloping leading and trailing edges, the triggering voltages can be adjusted to produce output marking and spacing pulses of equal width, or widths of predetermined ratio, as indicated in connection with Figs. 2, 3, 4 (not shown).