4-Wire Pax Connection With E&M Signalling; 2/4-Wire Pax Connection With E&M Signalling And Hybrid Control; Fig. 3-29 4-Wire Pax Connection With E&M; Fig. 3-30 2/4-Wire Pax Connection With E&M And Hybrid Control - ABB ETL600 Instruction Manual

ABB Switzerland Ltd
3.4.1.3. 4-wire PAX connection with E&M signalling
PAX
Fig. 3-29
In this application, the ETL-link is inserted into a 4-wire trunk line as
shown in Fig. 3-29.
Signaling is done via E- and M-wires. In order to improve the signal to
noise ratio by up to 10 dB on noisy links, a compander function can be
enabled. The compander can be activated permanently or it can be
controlled by the input 'Local/Transit' driven by the PAX. A galvanically
isolated relay switch-over contact 'PAX blocking' indicates, if the
speech channel of the PLC link is interrupted or distorted by excessive
line noise. During these periods, E&M signaling is not available and
the speech signal is squelched. All three signals: E-wire, M-wire and
Local/Transit can be inverted independently. All signaling wires are
galvanically isolated. The PAX only needs a dry relay contact to
control M-Wire and Local/Transit input, since ETL600 provides an
extra voltage source for these inputs.
As long as the trunk line is idle, the service phone may utilize the
speech channel. In any case, the trunk line has priority over the
service phone. To determine whether the trunk line is busy, the states
of E- and M-wires are monitored: If at least one of these is in the active
state, the trunk line is considered busy.
3.4.1.4. 2/4-wire PAX connection with E&M signalling and hybrid control
PAX
Fig. 3-30
In this application, a 4-wire as well as a 2-wire circuit is provided. The
PAX selects one of the two circuits depending control input
'Local/Transit' of the O4LE board carrying the service. This type of
operation may be required with older PAX's that use 4-wire circuits for
transit connections and 2-wire circuits for local subscriber connections.
It should be noted that the 2-wire Rx path is always connected
independent of the condition of the 'Local/Transit' control line.
Therefore, speech and signaling tones can always be received at the
'PAX2W' terminals. When the circuit is busy, the E- and M-wire are
active. It is also possible to control the compander with the
'Local/Transit' line. Since the best intelligibility improvement is obtained
3-40
1KHW001489-EN
ETL600
Local/Transit
E&M, PAX Blocking
O4LE
4
4-wire PAX connection with E&M
ETL600
Local/Transit
E&M, PAX Blocking
O4LE
4
2
2/4-wire PAX connection with E&M and hybrid control
November 2005
ETL600
ETL600
Local/Transit
E&M, PAX Blocking
O4LE
4
ETL600
Local/Transit
E&M, PAX Blocking
O4LE
4
2
Structure and Function
PAX
PAX