Improvements in or relating to receiving arrangements for teleprinter signals

666,231. Code telegraphy. STANDARD TELEPHONES & CABLES, Ltd. Sept. 24, 1948, No. 25007/48. Class 40 (iii). A telegraph receiver for marking and spacing teleprinter signals comprises a two-condition electronic trigger device employing first and second thermionic valves each including a screen grid and a suppressor grid and each having its anode cross-connected to the screen grid of the other valve so that conduction of either valve cuts off the other, means for applying input marking and spacing signals to said device to cause the conduction respectively of said first and second valves and means for applying a negative impulse to the suppressor grid of said second valve shortly after the cessation of input signals to trigger said device into the marking condition, if not already in that condition. In the circuit arrangement shown, a negative spacing impulse applied to the grid of the pentode 3 renders the valve non-conducting and makes valve 4 conducting and a subsequent marking impulse applied to the valve 3 reverses the condition of the valves. The impulses derived from the anode circuit of the valve 3 are fed via a D.C. amplifier 12 to an output terminal 13. The output from the amplifier 12 is also fed through a blocking condenser 18 and a rectifier 19 poled so that a condenser 21 is charged negatively and cuts off a triode valve 14. When signals have ceased the condenser 21 discharges through a resistance 20 which is short circuited by a rectifier 23 during the charging operation. The discharge of condenser 21 allows the valve 14 to conduct and apply a negative pulse to the suppressor grid of the valve 4 which is made non-conducting if it had not been left in that condition. The cutting-off action of the valve 4 also applies a positive pulse to the grid of the valve 14 which accelerates the pro- - cess of the cut off of the valve 4. The resistance 20 is such that the condenser 21 discharges more slowly than it was charged. A rectifier 25 prevents the suppressor grid of the valve 4 from acquiring a positive charge. The mark-to-space rates of the output signals can be varied by an adjustable tapping point on a potentiometer resistance 5 connected across the equal anode load resistances 6, 7 of the valves 3, 4. The input signals at the terminals 1, 2 may be derived from a frequency-modulated transmission system. Specification 652,154 is referred to.