T-Home Comfort Pro S, Installation Manual

Page: 114 / 168

112
PBX Networking Connections
Example of a PBX network
Various line types and transmission protocols can be used for point-to-point connections. The required
network topology (distance, connection capacity) determines which type of point-to-point connection is most
suitable.
A Q.SIG-IP network connection can be established using a fast VPN connection. When the connection is via
internet, encryption is advisable for security reasons.
Protocol: Q.SIG or DSS1
The Q.SIG protocol, designed for ISDN point-to-point connections, is the preferable choice as the trans-
mission protocol; alternatively, the DSS1 protocol, designed for ISDN dial-up connections in the Euro-ISDN,
can be used. Certain PBX networking features can only be used with the Q.SIG/Q.SIG-IP protocol, however. In
particular, the identifier indicating whether a call is internal or external cannot be transmitted using DSS1.
Both protocols implement communication on several protocol layers:
■
L1: Layer 1 defines the physical line properties and the electrical coding of signals.
■
L2: Layer 2 enables communication via individual error-protected channels that are independent of each
other.
■
L3: Layer 3 defines the administration of the individual channels and implements the features designed
for ISDN.
N
Note: All layers of the Q.SIG-IP protocol are symmetrical. The following are unneces-
sary: a Master/Slave setting, clock and synchronisation settings (please refer to
Connection via Q.SIG.IP starting on page 116).
Point-to-point
connection
Trunk line
PBX PBX PBX PBX
PBX