Introduction To Line Telecommunications

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6. Private Circuit Links
  6.1 - Private Wires And Access Lines
  6.2 - Leased Lines
  6.3 - Digital Leased Lines

6.2.2 - DC10

Also known as Signalling System Direct Current No. 10 (SSDC10) this is another short distance PBX interlinking system. The link is a 2 wire system , A and B, with signalling being achieved by application of combinations of negative battery voltage, earth and loop (A and B connected together) to the wires along with two way speech. The battery voltage is usually 50 volts.

The table below shows the conditions applied to the wires during the various stages of a call. In some cases the duration of the condition is important and in such cases the duration is also shown.

Outgoing End Incoming End
Idle Loop Loop Loop Loop
Seizing Earth - V - -
Delay Dial - - Earth Earth
Proceed To Dial - - Loop Loop
Dialling - V Earth Pulses - -
Answer - - Earth Earth
Forward Hold Earth - V - -
Backward Hold - - Earth Earth
Forward Clear - V Earth >300ms - -
Backward Clear - - Loop >300ms Loop >300ms
Forward Aux - V Earth 45 -135ms - -
Backward Aux - - Loop 45 -135ms Loop 45 -135ms
Table 2 - DC10 A And B Wire States

The Delay Dial, Proceed To Dial and Aux signals are optional and will not be used on all links of this type.





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Introduction To Line Telecommunications
Copyright Panasonic Business Systems UK Ltd 2000