Preliminary
PBL 386 65/2
4. The overload level is automatically expanded, as needed
up to 3.1 VPeak when the signal level >1.55 VPeak and is
specified at the four-wire transmit port, VTX, with the signal
source at the two-wire port. Note that the gain from the
two-wire port to the four-wire transmit port is G2-4S = 0.5.
5. Secondary protection resistors RF impact the insertion loss
as explained in the text, section Transmission. The
specified insertion loss is for RF = 0.
Notes
1. The overload level is automatically expanded when the
signal level > 3.1 VPeak and is specified at the two-wire port
with the signal source at the four-wire receive port.
2. The two-wire impedance is programmable by selection of
external component values according to:
ZTR = ZT/|G2-4S
α RSN| where:
ZTR = impedance between the TIPX and RINGX
terminals
ZT = programming network between the VTX and RSN
terminals
6. The specified insertion loss tolerance does not include
errors caused by external components.
7. The level is specified at the four-wire receive port and
referenced to a 600 Ω programmed two-wire impedance
level.
8. The two-wire idle noise is specified with the four-wire
receive port grounded (ERX = 0; see figure 6).
The four-wire idle noise at VTX is the two-wire value -6 dB
and is specified with the two-wire port terminated in 600 Ω
(RL). The noise specification is referenced to a 600 Ω
programmed two-wire impedance level at VTX. The four-wire
receive port is grounded (ERX = 0).
G2-4S = transmit gain, nominally = 0.5
α
RSN = receive current gain, nominally = 400 (current
defined as positive flowing into the receivesumm-
ing node, RSN, and when flowing from tip to ring).
3. Higher return loss values can be achieved by adding a
reactive component to RT, the two-wire terminating
impedance programming resistance, e.g. by dividing RT
into two equal halves and connecting a capacitor from the
common point to ground.
R
S
TIPX
-48V
PBL 386 65/2
RLRTO
RINGX
Figure 7. Tipx voltage.
7
ERICSSON [ ERICSSON ]
