Datasheet

DS21352/DS21552
93 of 137
16.5 RECEIVE MONITOR MODE
When connecting to a monitor port a large resistive loss is incurred due to the voltage divider between the
T1 line termination resistors (Rt) and the monitor port isolation resistors (Rm) as shown below. The Rm
resistors are typically 470 ohm. This, along with the 100 ohm termination (Rt), produces 20dB of loss.
The receiver of the DS21352/552 can provide gain to overcome the resistive loss of a monitor connection.
This is a purely resistive loss/gain and should not be confused with the cable loss characteristics of a T1
transmission line. Via the TEST2 register as shown in the table below, the receiver can be programmed
to provide both 12dB and 20dB of gain.
Figure 16-8 TYPICAL MONITOR PORT APPLICATION
Table 16-5 RECEIVE MONITOR MODE GAIN
TEST2 (Address = 09 Hex) Register Value Gain
72 Hex
12dB
70 Hex 20dB
PRIMARY
T1 TERMINATING
DEVICE
MONITOR
PORT JACK
T1 LINE
X
F
M
R
DS21X52
Rt
Rm Rm
SECONDARY T1
TERMINATING
DEVICE