PBL 386 14/1
Notes
1.
The overload level is automatically expanded to 2.5 V
Peak
when the signal level > 1.0 V
Peak
and is specified at the
two-wire port with the signal source at the four-wire
receive port.
The two-wire impedance is programmable by selection of
external component values according to:
Z
TR
= Z
T
/|G
2-4S
α
RSN
| where:
Z
TR
= impedance between the TIPX and RINGX
terminals
Z
T
= programming network between the VTX and RSN
terminals
G
2-4S
= 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).
Higher return loss values can be achieved by adding a
reactive component to R
T
, the two-wire terminating
impedance programming resistance, e.g. by dividing R
T
into two equal halves and connecting a capacitor from the
common point to ground.
4.
The overload level is automatically expanded as needed up
to 1.25 V
Peak
when the signal level >0.5 V
Peak
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 G
2-4S
= -0.5.
Secondary protection resistors R
F
impact the insertion loss.
The specified insertion loss is for R
F
= 0.
The specified insertion loss tolerance does not include
errors caused by external components.
The level is specified at the four-wire receive port and
referenced to a 600
Ω
programmed two-wire impedance
level.
The two-wire idle noise is specified with the four-wire
receive port grounded (E
RX
= 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
(R
L
). The noise specification is referenced to a 600
Ω
programmed two-wire impedance level at VTX. The four-
wire receive port is grounded (E
RX
= 0).
The V
Bat2
voltage is optimized for R
L
=600
Ω
with a
programmed linecurrent, I
L
=27 mA. This gives V
Bat2
=22 V at
the terminal (e.g. calculated to 21.9V).
2.
5.
6.
7.
8.
3.
9.
7
ERICSSON [ ERICSSON ]
