Appl. No.: 661,999
 Filed: Mar. 1,1991
 Foreign Application Priority Data
Mar. 2, 1990 [FR] France 90 02629
 Int. CI.5 H04H 5/00
 U.S. Q 381/3; 381/2;
455/3.2; 455/51.1; 375/107; 370/100.1
 Field of Search 381/2, 3; 455/3, 6,
455/51, 3.2, 6.2, 51.1; 375/107; 370/100.1
 References Cited
U.S. PATENT DOCUMENTS
4,317,220 2/1982 Martin .
4,608,699 8/1986 Batlivala et al. .
4,688,210 8/1987 Eizenhofer et al 375/107
4,821,260 4/1989 Klank et al 381/2
4,972,410 11/1990 Cohen et al 455/51
5,038,402 9/1991 Robbins 381/2
FOREIGN PATENT DOCUMENTS
2001230 1/1979 United Kingdom .
Primary Examiner—Jin F. Ng
Assistant Examiner—Edward Lefkowitz
A synchronized broadcast network comprises a main transmitter transmitting an audio source signal to a plurality of receiver/transmitter units remote from each other and from the main transmitter, the receiver/transmitter units broadcasting the audio signal using frequency modulation. In the main transmitter the audio source signal is digitized by sampling it at a predetermined sampling frequency. A digitized signal representing the sampled audio signal is transmitted to the receiver/transmitter units. In each receiver/transmitter unit a reference signal representing the sampling frequency is derived from the received digitized signal and the received digitized signal is passed through a succession of digital processing stages including a stage in which a carrier derived from the reference signal is digitally modulated and a stage in which the result of the digital modulation is digital-to-analog converted. In one of the digital processing stages the received digitized signal is delayed for a predetermined time in order to synchronize the phase of the receiver/transmitter units. All the digital processing stages are synchronized to the reference signal to obtain identical digital modulation of the same carrier for all the receiver/transmitter units. The result of the digital-to-analog conversion stage is transposed to a final frequency derived from the reference signal for broadcasting the analog audio signal using frequency modulation with the same modulation, phase and carrier at all receiver/transmitter units.
4 Claims, 6 Drawing Sheets