5.8.9. Connection to External Systems Using TC-SL Link 
Straightforward networking of the OpenScape 4000 with external products
is possible with a TC-SL link. An analog subscriber line (SL) from the
external system is connected to a trunk circuit (TC) from the OpenScape
4000 (loop start signaling).
The following chapters contain some specific notes on the following applications:
- Outgoing seizure
- Incoming seizure
- Consultation hold
- Trunk grounding/trunk flash
- Consultation hold pick up in straightforward trunk calls
- Suffix dialing