| 摘要 |
In the intercom system, which serves in particular for use as a door intercom system, groups in each case comprising n = 22 extensions (CIT 1/1, CIT n/1, CIT 1/2, CIT n/2) are connected, each group being connected via only two common wires (LNC, LN/1; LNC, LN/2) to the main station (left side of the figure). This is possible because the called extension is selected by adding the half-waves of a ringing and actuation frequency, a characteristic frequency being allocated to each extension (CIT). <IMAGE>
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