Speech Bandwidth; Guard Signal - ABB ETL600 Instruction Manual

ETL600
In conjunction with one APLC channel, the DPLC channel requires its
own guard signal for the NSD600 (which is not necessary without TPE
in the DPLC).
A detailed description of the ETL600 operating principle and the
various channel allocations can be found in sections 3.1 and 3.2.
3.6.8.2.

Speech bandwidth

The NSD600 supports all programmable speech channels (2.0, 2.2,
2.4, 2.6, 2.8, 3.0, 3.2 and 3.4 kHz) when using the ETL600 pilot as a
guard signal. The trip frequencies are always transmitted in the band
0.3 ... 2.0 kHz. Adequate filtering is performed to separate the band
from superimposed teleoperation channels.
An own guard signal is only provided for the following speech
channels: 2.0, 2.2 and 2.4 kHz.
To avoid additional transmission delays, the non-equalized receive
signal is used for processing the NSD600 tripping signals.
3.6.8.3.

Guard signal

Default setting for the NSD600 guard signal is the ETL600 pilot at
3840 Hz. The disposable teleoperation band is then limited from 120
Hz above speech up to 3600 Hz.
If the ETL600 pilot signal is shifted from its default value to lower
frequencies, teleoperation channels may only be allocated with a
frequency margin of ± 240 Hz from the centre of the pilot channel.
For special purpose, e.g. transit relaying of NSD600 signals in a
repeater station, a separate guard signal for the teleprotection may be
programmed. It is then located above the chosen speech frequency
band. This is however possible only for the following speech channels:
2.0, 2.2 or 2.4 kHz.
A gap of 480 Hz has to be reserved for the own guard signal of the
NSD600. The disposable teleoperation band is therefore limited from
480 Hz above speech up to 3720 Hz.
If no speech is configured in the APLC channel, the own guard signal
is allocated in the band 2000 Hz to 2480 Hz.
The performance figures NSD600 for security, dependability and
transmission time are almost equal when using an own guard signal or
when using the ETL600 pilot as a guard signal.
The nominal guard signal level depends on the configured services (S-
value) minus all not disconnectable signals. Its minimum level is
-6 dBm0.
Structure and Function
1KHW001489-EN
November 2005
ABB Switzerland Ltd
3-73