26
SEL-FT50/SEL-FR12 Fault Transmitter and Receiver System
Instruction Manual
Date Code 20210405
Device Installation
played if weak signals are arriving from distant devices. As each SEL-RP50
starts repeating the Link messages the RSSI reading might jump to a higher
value. If you set the Gain switch to the High position based on these early read-
ings, the signals from the closest SEL-RP50s might be too strong to be received.
This is unlikely if the SEL-RP50s are installed according to the guidelines in
Appendix D: SEL-RP50 Fault Repeater Detailed Implementation on page 54
.
Receive Signal Strength Indicator
The SEL-FR12 has a built-in feature to determine the link quality for each of its
12 SEL-FT50/SEL-FR12 links called Receive Signal Strength Indicator (RSSI)
mode. While in Normal mode, press and hold the
TARGET RESET
pushbutton for at
least four seconds (until the
ENABLED
LED begins flashing) to enter RSSI mode.
The SEL-FR12 will display the receive signal strength of each link as follows:
➤
The
ENABLED
LED blinks once per second to indicate that the device
is in RSSI mode.
➤
FAULT
LED 1 illuminates to indicate that you are reading the RSSI for
the link between the SEL-FR12 and the SEL-FT50 with Unit ID 1.
Press the
TARGET RESET
pushbutton to sequence through Unit IDs 1–12.
➤
The
LINK
LEDs report the RSSI as shown in
Table 5
and
Table 6
. The
SEL-FR12 receive sensitivity is specified with one percent packet
error. If the SEL-FR12 is receiving at or below its receive sensitivity,
no LEDs are illuminated. Each LED corresponds to a 2 dB increase
in signal strength above the threshold.
Figure 20
Trio Attenuation Switch Selection
Table 5
RSSI Specifications for FR12-0001/FR12-0003/FR12-0006 (U.S.A.,
Canada, Mexico, Peru, and Brazil)
Number of LINK LEDs Illuminated
RSSI (High Gain Mode)
a
a
For RSSI values in Low Gain mode, add 16 dB to each value.
0
–97 dBm or worse
1
–95 dBm
2
–93 dBm
3
–91 dBm
4
–89 dBm
5
–87 dBm
6
–85 dBm
7
–83 dBm
8
–81 dBm
9
–79 dBm
10
–77 dBm
11
–75 dBm
12
–73 dBm or better
NOTE:
The RSSI feature was
introduced in March 2018. Devices
with prior serial numbers will not
support the receive signal strength
feature.
NOTE:
The SEL-FR12 still supports
its normal M
IRRORED
B
ITS
communications operation even when
it is not in Normal mode (i.e., your
scheme will remain active).
NOTE:
RSSI readings are only
available by reading the front-panel
LEDs. They cannot be accessed
remotely.
