| 摘要 |
PURPOSE:To reduce the test time by providing two pairs of a DC superimposing circuit to be provided on the instrument side and a DC cut-off capacitor, using the one pair and keeping the other set in standby state so as to make a voltage across the DC cut-off capacitor stable before the measurement. CONSTITUTION:In connecting a subscriber circuit 1 and the DC superimposing circuit 1 by a channel selector CS1 at the start of test, the DC cut-off capacitor C1 is charged. After the voltage across the capacitor is made stable at a prescribed time after the start of charging, a transformer T1 and an instrument M are connected by a selector CS2 to measure the transmission characteristic of the subscriber circuit 1. In controlling the channel selector CS1 at the same time as the measurement to connect the next subscriber circuit 2 to the DC superimposing circuit D2, the charging of the DC cut-off capacitor C2 is started. When the measurement of the subscriber circuit 1 is finished, the channel selector CS1 is controlled to connect the DC superimposing circuit D1 to a subscriber circuit 3 and the channel selector CS2 is controlled at the same time to connect the instrument M to a transformer T2. In such case, since the voltage of the DC cut-off capacitor C2 is made stable, the measurement of the subscriber circuit 2 is conducted without any waiting time. Similarly, up to the subscriber circuit (n) is measured by controlling channel selectors CS1, CS2 sequentially.
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