Patent GB-809599-A (GB)
Title: Improved flight training apparatus for simulating radio station tuning
Inventor: GALLO JOSEPH EDWARD
IPC: G09B9/26
Filed: 1955-07-01
Abstract: 809,599. Radio training apparatus. CURTISS-WRIGHT CORPORATION. July 1, 1955, No. 19121/55. Class 40 (4). [Also in Group XL (c)] An apparatus for training radio operators comprises a device representing station frequencies preset by the instructor, a further device adjustable by the trainee, each of said devices emitting electrical signals in accordance with their setting, said signals being combined to operate an indicator in such a manner as to simulate an off-time condition in accordance with the difference in settings of the devices. As shown, Fig. 1, the devices 18, 29 set by the instructor and trainee respectively control potentiometers 16 and 26 which feed oppositelyphased A.C. to a summing amplifier 23. The negative output from the latter after rectification at 31 is smoothed at 33 and used to suppress a valve 36 fed with audio signals characteristic of the type of signals the trainee can expect to have to deal with. The output from valve 3 is amplified at 4 and fed to the trainee's earphones 5. Thus the valve 3 controlling the audio signal fed to the earphones progressively becomes more conducting and the audio signal louder as the simulated receiver is " tuned in ". Additional smoothing for the rectifier output may be obtained by means of the valve 36 fed by the residual ripple from the smoothing circuit 33, the output of the valve being combined in antiphase to the input signal for feeding to the valve 3. The amplifier 4, the earphones 5, and the trainee's potentiometer may be common to a plurality of pieces of apparatus each simulating a different transmitting station. The output from the rectifier 31 may also control a valve 76, so that when the station is " tuned in " a relay 45 operates to connect up direction-finding training apparatus, Fig. 2, (see Group XL (c)). In a second embodiment, Fig. 4, the instructor's and trainee's controls each comprise two potentiometers 110, 112 and 114, 115, the former of each pair being calibrated in " megacycles " and the latter in " tenths of megacycles ". The oppositely phased outputs from the " megacycles " potentiometers are added in amplifier V1 and the oppositely-phased outputs from the " tenth megacycles " potentiometer are added in valve V2 to which the output of V1 is also injected. The output from V2 after rectification suppresses the valve V4. When the simulated receiver is " in tune " V4 conducts to operate relay R to enable valves V5 and V6. Valve V5 may admit audio signals to amplifier 134 and thence to earphones 135. Valve V6 admits a signal simulating a flight deviation signal through an amplifier 140 to a visual indicator 139. To ensure that a possible difference between the " megacycle " potentiometer cannot be called out in valve V2 by an equal but opposite difference in the " tenth megacyele " potentiometer, the input to valve V1 contains a condenser 120 which introduces a phase shift as between difference voltages received from the two pins of potentiometers. Specification 611,403, [Group XL (c)], is referred to.