PBL 3766
This causes the SLIC to present a high
impedance to the line. Power dissipation
is at a minimum. No detectors are active.
Active State (C2, C1 = 1, 0)
VBat - 3 V
IL ≈
TIPX is the terminal closest to ground
potential and sources loop current, while
RINGX is the more negative terminal and
sinks loop current. Vf signal transmission
is normal. The loop current detector is
activated and connected to the DET output.
RL + 1800 Ω
where
Ringing State (C2, C1 = 0, 1)
IL = loop current (A)
VBat = battery supply voltage (V)
RL = loop resistance (ohm)
The ring relay driver, RINGRLY, is activ-
ated and the ring trip comparator is
connected to the detector out-put, DET.
The TIPX and RINGX terminals are in the
high impedance state and signal trans-
mission is inhibited.
Stand-By State (C2, C1 = 1, 1)
The short circuit loop current (ILSh) for
VBat = -48V is then limited to ILSh ≈ 25.0 mA.
The loop current detector is activated in
the stand-by state and is gated to the DET
output.
In the stand-by state the line drive amp-
lifiers are disconnected. The loop feed is
converted to resistive form according to
Table 1 summarizes the above
description of the control inputs.
C
R
RT
RT
R
1
DT 23/20
+
To DET
DR
-
R
2
V
EE
TIP
PBL 3766
E
RG
K
R
Figure 15. Example ring trip network,
unbalanced ringing.
V
Bat
RING
Note: Ericsson Components unbalanced
ring trip network PBA 3310 contains a
two-pole filter.
E
RG+
R
RT1
150Ω
DT 23/20
+
To DET
R
1
150kΩ
R
DR
2
-
150kΩ
R
150Ω
R
C
470nF
C
470nF
RT2
3
2
1
3.1MΩ
V
EE
E
RG-
-48V
-48V
TIPX
TIP
27/21
28/22
R
F1
Protection
R
F2
RINGX
RING
PBL 3766
K
R
Figure 16. Example ring trip network,
balanced ringing.
4-16
ERICSSON [ ERICSSON ]
