| 摘要 |
<p>An arrangement for selectively accessing and testing a digital telecommunications circuit (1) without detriment to the integrity of a signal carried thereby. The arrangement comprises an access unit (10) inserted in the circuit (1) to be tested, and test equipment (11) connected to the access unit (10) and through which the circuit to be tested can be selectively routed. The test equipment (11) includes a shift register (24) in its test circuit path. In order to match the delay introduced by the shift register (24) in the test circuit path, a similar clocked delay (21) is included in the access unit in the route followed by the telecommunications circuit (1) when undiverted. This delay matching avoids signal loss repetition when switching the circuit to be tested between its undiverted and diverted paths. Where the test equipment (1) is used to insert the test data into the diverted circuit, provision is made to avoid the introduction of bipolar-coding violations into bipolar signals carried by the circuit.</p> |
