Patent GB-383189-A (GB)
Title: Remote control system for radio receivers
IPC: H03J9/00
Filed: 1932-05-02
Abstract: 383,189. Wireless receiving apparatus. AXE, E. C., 27, Chancery Lane, London.-(Blatterman, A. S. ; 1304, Wannamassa Drive, Asbury Park, New Jersey, U.S.A.) May 2, 1932, No. 12577. [Class 40 (v).] A mains-driven radio receiver R, Fig. 5, of normal type is remotely controlled as regards station selection, volume, and on-and-off switching, by high-frequency currents transmitted along the supply mains L from any desired plug-point. The tuning of the radio set R is permanently fixed, preferably at one end of its tuning-range, and an adapter M comprising a mains-driven mixing or detecting valve T<1> is interposed between the aerial A and the set. A heterodyning or local oscillation is generated at the control point C by means of a mainsdriven valve oscillator T, and is sent along the supply mains L to the mixing-valve T<1>, which thus functions like a frequency-changing stage in a superheterodyne receiver. By the action of a relay 19 in the plate circuit of the mixing- valve T<1>, the radio set is switched on and off by the reception or non-reception of the local wave ; station selection is effected by varying the frequency of that wave ; and volume is regulated by varying its amplitude. The control apparatus C receives its power from a plug R<1> which when plugged in a socket S connects the transformer 36 across the mains L, energizes the cathodes of the valve oscillator T and the rectifier T<2>, and supplies high-tension direct current to the oscillator plate through the rectifier T<2> and smoother 45. The oscillator is tuned by a variable condenser 47 which thus forms the station selecting device ; and volume is controlled by a second variable condenser 52 interposed between the oscillator and the mains. Chokes 54, 55 prevent the oscillations from reaching the transformer 36, and a condenser 56 connected across the mains ensures that the mains act jointly as a single conductor for the oscillation, the return circuit being by accidental capacity to earth &c. A switch 9 is provided for stopping or starting the oscillator. The adapter M has terminals 5, 6 for the attachment of the aerial A and earth G<1>, and terminals 3, 4 for connection to the aerial and earth terminals 1, 2 of the radio set R. The mixer plug R<1> for insertion into mains socket S has one of its leads connected through a coupling-coil 68, supply transformer primary 59, and switch 71 to the earthed terminal 6, the other main being permanently earthed. The transformer secondaries supply the cathode heaters of a mixing or detecting valve T<1> and a supply rectifier T<3>, and the plate voltage of the rectifier T<3>. The latter through a smoothing circuit 81 and potentiometer 78 supplies D.C. voltage to the detector plate. The aerial A is tapped on the grid coil 74 of the detector, whilst the oscillatory current from the control apparatus C passes through the coil 68 inductively coupled to the grid coil 74. The resultant beat in the plate circuit is transmitted through a capacity 82 to the terminal 1 of the radio set R. Reception of the control oscillation reduces the detector plate current and the relay 19 releases its armature and completes the supply circuit for the set R through the plug R<1>, contact 19a, socket 86 and plug 85. In a modification, Figs. 4 and 6 (not shown), the control oscillator T is arranged to generate either a variable frequency (for station selection) or a separate fixed frequency (for on-and-off switching), according to the setting of a ganged switch. The relay 19 in the plate circuit responds only to the switching frequency, and is arranged to energize a stepping-magnet which by consecutive operations reciprocates a pawl on a ratchet wheel and rotates a cam. This cam is so shaped that consecutive positions open and close alternately a switch in the supply circuit of the set R.