662,520. Radio receiving systems. REUTERS, Ltd., BARTLETT, S. C., and STONOR, C. P. Oct. 10, 1949, No. 25980/49. Class 40 (v). In a remotely-controlled radio receiving system in which the receiving station is located away from a zone of severe interference where the signals are recorded, a single telephone line connects the two stations and the switching on and off of the receiver; the selection of any one of a number of pre-determined stations, fine tuning of the selected station, the adjusting of the R.F. gain and the switching in and out of the beat frequency oscillator are all controlled from the station where the signals are recorded. The line is also used to provide telephone facilities between the two stations. Fig. 1 shows the " master control unit " located at the recording station and Figs. 2, 3 and 4, the " receiver control unit," tuning head " and the motor-operated station selection switch, all of which are located at the receiving station. To select a received signal of predetermined frequency.-The " change frequency, stand-by key" K, Fig. 1, is moved to the middle " Receive " position when 50 volt D.C. is sent to the line at jack J1 and is received at jack J3, Fig. 2, of the receiver control unit. Impulsing relay A operates and positive battery is extended via rotary switch LEV1 to operate the slow-to-release relay B. Relay PR operates and switches on the receiver power pack and relay BR operates and operates the dialling relay C which operates relay CR. The D.C. sent to line from jack J1 is impulsed by dialling at O, Fig. 1, and the impulses are repeated by relay A. If, say, station 5 is required without the use of the B.F.O., code " 35 " is dialled, the wiper of the rotary switch is stepped forward three steps, during the inter-digital pause relay C is re-energized via winding cd and the wiper then steps forward a further 5 steps under the control of the dialled impulses. Relay C releases which releases relay CR and positive is extended via switch LEV3 to socket-pins B6 and B7 and thus to the tuning head motor (Figs. 3 and 4), negative is extended via socket pin B8. Motor M thus rotates and operates the switch YSS, Fig. 4, via the gear-box GB until contact 5 of switch A, Fig. 3, is found when positive battery is picked-up and is extended via B4 to operate relay SM, Fig. 2. The armature of the motor is thus short-circuited through a low resistance and as the field is still energized the motor is rapidly stopped. Positive battery is also extended from the wiper of switch LEV1 to operate relay HR which operates the rotary switch magnet DM, the interrupter springs INT then being opened so that the cycle is repeated and the rotary switches step on until the contact 14 is reached, when relay HR releases and the rotary switches stop. As switch LEV2 is on contact 14, there is no resistance between terminals C3 and C4 so that the R.F. gain of the receiver is at a maximum. The receiver will now be correctly set to station 5 and its audio output is fed via jack J1 to the outgoing telephone line at jack J3 and may be monitored at jack J2. At the controlling end the incoming signal is monitored at jack J2 and is fed to the recording instrument at jack J3. To effect fine tuning of the receiver.-Fine tuning of the receiver is effected by varying resistors R1, R2, Fig. 1, which controls the value of D.C. current passed to line. At the receiver end the resultant potential across the ring type rectifier TMR is applied via leads x, y and terminals C7, C8 to the tuning head (Fig. 3) where it is measured by the tuning meter TM which also acts as a variable capacitor across the oscillator coil of the receiver. The movement of the pointer of the meter varying the effective capacity to effect fine tuning of the receiver. To control the B.F. gain of the receiver.-When a given incoming station is selected and with the rotary switches on contact 14 the R.F. gain is a maximum, the dialling of successive single impulses steps on the switches one step at a time so that increasing values of resistance are included via terminals C3, C4 in the cathode circuit of the R.F. valves of the receiver and the gain is successively reduced. To switch in the beat frequency oscillator.-If the B.F.O. is now required, key K, Fig. 1, is depressed, thus removing the D.C. from line and releasing relay A, Fig. 2. Relay B releases and thus releases relays PR, BR and SM. The positive battery on rotary switch LEV1 is extended to relay HR which operates so that the rotary switches step round as already described until the switch LEV1 reaches the position shown in Fig. 1, when positive battery is removed from relay HR and the switch comes to rest. Key K, Fig. 1, is returned to its position shown and code " 215 " is dialled as station 5 with B.F.O. is required. The rotary switch steps round to contact 3 and during the inter-digital pause relays C and CR release and negative battery is extended via resistor R16 to operate relay BFO which switches on the B.F.O. via contacts 9, 10. The digit " 1 " is now dialled, the rotary switches move on to position 4 and on the dialling of digit 5 the required station is selected. To effect speaking and ringing over the circuit.-The master control operator cancels any existing selection by operation of key K and " 1 " is dialled, the rotary switch steps one contact forward, C relay releases and then relay CR and negative battery is extended to the " d " coil tag of relay RR, positive being extended to the " a tag via switch LEV4. Relay RR therefore operates and bell RB is sounded. The telephone key TK at the receiver position is moved to " speak " which releases relay A and homes all the rotary switches, the operator plugs in his hand microphone and headphones and is connected to the master control operator who has thrown his key to the " telephone " position. The receiving station may ring the master station by moving the telephone key to " ring " which sends D.C. to line, relay TR, Fig. 1, is operated and sounds the associated bell. Local selection facilities at the receiver.- Selector switch LSY, Fig. 2, is set to select a given station, key LSK is operated which operates relay LSR and the motor M, Fig. 4, hunts until the selected contact is found.