Abstract: A radio warning receiver has a battery or accumulator (7) and means (8) for switching over to battery operation mode when network power (6) fails. Battery power is conserved by turning off (9) power to the end stage (3), placing the warning receiver in a so-called Stand-By Mode, until a control signal is detected (5) which indicates that a warning is to be broadcast. Then, power to the end stage is restored (11) for the duration of the warning broadcast.

Abstract: A warning broadcast system features control signal means, preferably digital, for confirming transmission path integrity prior to broadcast of a spoken warning message. A radio receiver (1) in an alarm center has an auxiliary carrier reception stage (4) which feeds a decoder (5). A coincidence circuit (6) has a first input (7) connected to the decoder output for inputting the received broadcast control signal and a second input (8) for inputting a directly-coupled control signal via a delay line (9) from the control signal generator (10) of the alarm center. When the control signals at the imputs (7, 8) of the coincidence circuit (6) coincide, an output signal (14) actuates a release (15) for the spoken warning message. If a plurality of transmitters (3) having different frequencies are networked, separate receivers (1,1', . . . ) set to the respective frequencies can feed their respective outputs (14, 14', . . . ) to an AND-gate (16) which triggers release (15).

Abstract: A programming unit (1) for ON-OFF switching of a siren or similar warning device can be provided with remote actuation capability by connecting it to a radio receiver tuner (27) and radio data signal decoder (25). The output of the signal decoder (25) is connected to a block decoder (12). Some of the block decoder outputs are connected to a comparison circuit (8) which attempts to match a broadcast siren address with a stored address uniquely identifying the associated siren program unit (1). In the event of a match, a set of flip-flops and gates controls loading of information at other block decoder outputs into a siren program buffer memory (4) and then into an end memory (3) attached to and controlling the program unit (1). After a siren program is performed, end memory (3) is reset.

Abstract: To decode control signals from a mixture of signals including audio signals, such as music, voice or speech, in which the control signals are within the audio range, for example 2,350 Hz, on which a low-frequency signal, for example in the 100-200 Hz range is modulated, the control signal in the form of a control tone is filtered and demodulated by band pass filters (1,3), demodulators and rectifiers (2,4), and then applied to a timing circuit (5) which provides an output signal if and only if the demodulated control tone is continuously applied during the timing interval thereof. Suitable timing intervals are about 1 second, to provide an output signal which can switch a flipflop (7) on, for example to command radiation of a particular type of recognition signal by the transmitter (13), the setting of the flipflop (FF) (7) being fed back to the timing circuit to change the timing interval thereof to a lesser amount, for example 1/2 seconds, to provide for a shorter signal to cause resetting of the FF (7).

Abstract: To permit mass-production of coders selectively usable in various types of transmitter installations, and regardless of whether designed for stereophonic or monophonic transmission, in which a subcarrier of non-audible frequency (57 kHz) is radiated, amplitude modulated by separate recognition signals characterizing intelligence information (AR, or announcement recognition) and a specific transmitter (region or radio station recognition, RR), a memory element (36) such as a PROM is provided, connected to a selector switch, the memory element having stored therein data representative of(1) frequency of amplitude modulation of the subcarrier of the announcement recognition (AR) signal;(2) frequency of amplitude modulation of the radio station recognition (RR) signal;(3) degree of modulation by the (AR) signal;(4) degree of modulation by the (RR) signal, and,preferably, data to provide a visual indication of a respective frequency channel and modulation degree, the memory element (36) being programmed for select

Abstract: A frequency recognition circuit includes a first phase locked loop to detect the carrier tone frequency, which locks to the detected frequency and provides the frequency-modulation frequency to a second PLL for modulation frequency recognition. When the predetermined carrier and modulation frequencies are recognized, an AND-gate provides a signal that removes a short-circuit from a capacitor that then begins to charge through a time constant circuit. The time constant circuit triggers a threshold switch after a period determined as the minimum duration for a signal and the threshold switch operates to advance a flipflop which performs a switching function and, at the same time, changes the time constant circuit so that the threshold switch will operate the next time on a signal of a different minimum duration. The decoder is designed to switch the output of a radio receiver on and off for selectively listening to traffic announcements.