| 摘要 |
<p>Time base circuit connected to a public telephone network by at least one link and operating regardless of the state of the link(s). According to the invention it comprises at least one module (1) connected to three buses (3, 4, 5), comprising: - means (110) for extracting a first synchronising signal from the signal transmitted by the said link when the latter is activated, - means (15) delivering a second synchronising signal, - means (14) emitting a signal proportional to the difference in phase between the said first and second synchronising signals, - means (19) for emitting a reference signal, - means (13) driven by the said proportional signal and whose output signal drives the said means (19) for emitting a reference signal, and the said means (15) delivering a second synchronising signal, - means (12) for transmitting to the first bus (5) the first synchronising signal when a link is activated, or the second synchronising signal when no link is activated, - means (18) delivering a signal indicating correct or incorrect functioning of the module, - means (16, 17, 11) for allowing transmission of the reference signal to the second bus (3) and of the second synchronising signal to the third bus (4) only when the said module is not defective, all the means (110, 12, 13, 15, 18, 19) being connected to a local bus (10). Preferably, the time base circuit comprises at least two identical modules (1, 2) connected to three common buses (3, 4, 5), one module being chosen as driver, the means (18) furthermore permitting another module to be made driver when the driver module is defective. Application to telephony. <IMAGE></p> |
