US2183931A - Wired radio change-over system - Google Patents

Description

H. R. 'BUTLER `WIRED RADIO CHANGE-OVER SYSTEM Dec. 19, 1939.

Filed March 3, 1958 munom 22.51522 zmwmmm mii INVENTOR Patented Dec. 19, 1939 UNITED STATES i 'amasar WIBED RADIO CHANGE-OVER` SYSTEM,

Henry R.. Butler, Verona, N. J., assigner to Wired Radio, Inc., New Turk, N. Y., a corporation o! Delaware Application March 3,1938, serial No. 193,646

-s claims. (ci. 11s- 15) This invention relates in general to a signalling system and especially relates to an arrangement for interposing special signals on a multi-program transmission system. The principal object of the invention consists in `providing a system for normally transmitting programs with' means for interposing on said system a special signal, such as an alarm, instructions, or the like, in cases of emergency or necessity,

A further object of the invention comprises providing a multi-channel program system for tra'ns- :mitting programs at a vplurality of diiferent frequencies to selective receivers with'means for.

interposing a special signal on all of said program channels so that a receiver tuned to any one of the program channels will receive a special signal. These and other objects will be apparent from the following, reference being had to theaccompanying drawing which represents one embodiment of the system of the invention.

' The invention will be described in connection with a wired radio system, although it will be apparent that other forms of signalling systems can equally well adopt the concept of the invention.

According to the invention, a base frequency source i, such as an electron tube oscillator, supplies a sustained high frequency wave of a base frequency such as, for` example, 13 kiloc'ycles.

This wave is fed to a harmonic generator 2 which develops a plurality of harmonic waves of different frequencies from the base frequency wave. These frequencies, such as 26, 39, 52, and 65 kilocycles, are respectively supplied to modulators s` 3 6. The modulators 3-6 comprise electron circuit means known-in the art for modulating high frequency waves with signals. The modulators 3-'6 have their input circuits connected to double pole switch arms 1-l0. These switch arms are 40 shown contacting terminals connected with modulation sources i-I-I 4 respectively. The switches may be moved commonly to engage other Vterminals connected in parallel with an emergency modulation source I5. Accordingly, it will be 45 seen that the modulators 3-6 may be connected either with the modulation sources I I-ll respectively, or in common with the emergency modulation source I5.

The output circuits of modulators vIi6 are 50 directed through power amplifiers IG--liiand thence through lters 2li-23. The lters 20-23 restrict the respective outputs to discrete fre- -quency bands impressed' through capacitive couplings upon the transmission medium 25. The

transmission medium 25 here shown is a commercial power distribution network connected with receivers having selective filter circuits and receiv'ing any one of the program channels trans- Y mitted through the various lters. The modula' tion sources iI-M comprise different program 5 `sources for supplying various program signals to the different modulators. The emergency modulation source l5 supplies emergency or predetermined signals. Itmay be provided with a phonograph for supplying prel0 determined Isignals at predetermined times, as controlled by a clock driven switch, or may be provided with a microphone such as microphone 26, under control of an emergency operator. The emergency operator might be the captain of a l5 ship, the superintendent of a building, or the chief of police or re chief of a township, who makes an announcement of vital importance to the receivers connected with the transmission medium 25.

As shown in the drawing, the microphone cir- 20 cuit includes a transformer connection 2 to a rectier-relay'28 which, upon being energized by signals in the transformer ZTI, operates a power relay to operate a slow-'to-release electromagnet 29' controlling an armature Si) mechanically con- 25 .nectd with `switch arms i-m When the electromagnet 29 is energized, the switches ie-l@ are pulled against tensioning spring 3i so asto engage contactsv connected with emergency modulation source .i5 and thereby connect all of'modu'lators 30 3 6 in common with the emergency modulation source so that the emergency signals are transmitted over the transmission medium. Thus, no matter to what program signal the receivers are tuned, they will receive the emergency signals. The electromagnet 29 will not release the switch arms 1-I0 until a predetermined time has lapsed after energization of transformer 21 by the emergency signals.

Although a preferred form of system has been 40 disclosed, it will be recognized that various changes and modifications can be made by those skilled in the art without departing from the intended scope of the invention. Therefore, no limitation is intended except as pointed out in the appended claims.

What is claimed as new and original to be secured by Letters Patent of the United States is: l

1. A signalling system comprising, a common transmission medium, transmissionmeans for transmitting a plurality of different programs'at discrete frequencies over said transmission medum, an emergency modulation source, and control means for interrupting said program transmission and` connecting said emergency modulation sourcewwith said transmission means to simultaneously transmit the single emergency signal modulation at all of said frequencies, said emergenoymodulation source comprising means responsive to the emergency modulations for ac- -tuating said control means.

2. A signalling system in accordance with claim 1 in which said transmission means includes a plurality of modulators and a plurality of modulation sources respectively connected to said modulators in normal operation, and in which said control means is adapted to disconnect all said modulation sources from said modulators and connect said emergency modulation source in common with all of said modulators.

3. A signalling system in accordance with claim 1 in which said transmission means inciudes means -for generating a plurality of harmonically related discrete carrier frequencies, a plurality of diierent modulation sources, a plurality of mod- -ulators for respectively modulating said diierent carrier frequencies with the modulation signals i from said diierent sources, and in which said cuits of, said modulators, connections .to said switches for connectingl said program modulation sources respectively with said modulators or for connecting said emergency modulation source in common with all of said modulators for transmitting an emergency modulation signal at all of said discrete carrier frequencies, and means responsive to the emergency modulations for operating said switches to effect immediately said common connection and return to said respective connections a predetermined period after cessation of the emergency modulations.

5. A signalling system in accordance with claim 4 including electromagnetic means for controlling said switches, and circuits extending from said emergency modulation source to said electromagnetic means for `controlling the same to tiein said emergency modulation source with all of said modulators.

6. In a system for transmitting a plurality of carriers over a wire network to a multiplicity of receivers, each carrier being modulated by a separate program source in normal operation, a cutin device comprising, a source of special modulations, a relay actuated by said modulations, and a switch operative in response to said relay for disconnecting all said program modulation sources and connecting saidspecial modulation source to all said carriers immediately upon the occurrence oi special modulation, said switch being adapted to hold the latter connection for a predetermined time after cessation of said relay actuation.

Y HENRY R. BUTLER.

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