RFL 9506 Operating and maintenance instructions

POWER-LINE CARRIER SYSTEMS
TYPE RFL 9506
GENERAL DESCRIPTION
Rev. 8’ October 2001

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TABLE OF CONTENTS
Page
INTRODUCTION 1
1CONSTITUTION OF THE SYSTEM 2
1.1 TYPES OF TERMINALS 2
1.2 OPTIONAL SERVICES 3
2PARTICULARITIES OF THE SYSTEM 4
2.1 MODULATIONS AND DEMODULATIONS 4
2.2 USE OF THE BASE BAND 10
2.3 USE OF THE PILOT CHANNEL 10
3PROGRAMMING, CONFIGURATION AND SUPERVISION OF THE SYSTEM 13
3.1 CONFIGURATION AND PROGRAMMING MENU 15
3.2 SUPERVISION MENU 16
3.3 COMMISSIONING HELP MENU 18
4CONSTITUTION OF THE TERMINAL 19
4.1 MODULES FOR THE BASIC EQUIPMENT 19
4.2 MODULES FOR OTHER VERSIONS 22
4.3 OPTIONAL MODULES AND SUBMODULES 23
4.4 BUILT-IN EQUIPMENT 25
5TECHNICAL CHARACTERISTICS 26
5.1 GENERAL CHARACTERISTICS 26
5.2 HIGH-FREQUENCY CHARACTERISTICS 28
5.3 AUDIO-FREQUENCY CHARACTERISTICS 29
5.4 OPERATING CONDITIONS 32
5.5 MECHANICAL CHARACTERISTICS 33
5.6 CHARACTERISTICS OF THE PROGRAMMING TERMINAL 34
6CONSTRUCTIVE CHARACTERISTICS 35

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INTRODUCTION
The RFL 9506 Power-Line Carrier (PLC) system allows one or two standard 4kHz
channels to be transmitted over high-voltage lines. The effectively transmitted frequency
band of these channels is situated between 300 Hz and 3850 Hz.
RFL 9506 terminals constitute an extremely versatile system, in which the most important
parameters such as transmission frequencies, input and output levels, modulation
percentages and so on can be fully programmed from a compatible PC or from a dedicated
console.
The equipment features a supervision system that gives access to any of the terminals of a
link comprising RFL 9506 equipment, from a PC connected to any of these terminals via
an RS-232C interface, in order to collect information regarding the noise level, the received
pilot level, the chronological list of alarms and so on.
Supervision as well as programming from a distance can be carried out by means of the
internal 50 Bd channel used to transmit the call and carry out the Automatic Gain Control
(AGC) of the receiver.
The technology used in the design of the RFL 9506 is based on microprocessors, on digital
signal processing, and on high-performance filtering by means of active components and
switched-capacity devices. Thanks to the use of the most advanced devices in the process
of signal synthesis, the definition of the transmission and reception frequencies can be
carried out in 1 Hz steps.
The modular construction of the equipment permits its configuration and its characteristics
to be easily adapted to the particular requirements of communication networks.
RFL 9506 terminals comply with the International Recommendation IEC 495, regarding
PLC equipment.

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1CONSTITUTION OF THE SYSTEM
The RFL 9506 system comprises terminals that offer a wide range of possibilities for PLC
transmission. The terminals can be equipped with a series of options that allow the
equipment to be adapted for the transmission of information required by electricity
companies, as well as for communicating over a power network.
1.1 TYPES OF TERMINALS
The RFL 9506 system features terminals of one or two standard 4 kHz channels and can
have an output power of 5W, 20 W, 40 W or 80 W (PEP), measured at the
coaxial-connector output. This power can be increased, depending on the channel
frequency, up to a value between 150% and 280% for a period of no more than 500 ms in
order to transmit a teleprotection command (overboosting).
Each channel can be used for speech-plus transmission or exclusively for data
transmission. The effectively transmitted frequency band of the channel, which is to say
the available band, extends between 300 Hz and 3850 Hz.
Four models of RFL 9506 terminals are available, each with a different output power.
These models are: RFL 9506-05, RFL 9506-20, RFL 9506-40 and RFL 9506-80 the output
power of which is 5 W, 20 W, 40 W and 80 W respectively.
The simplest version of each model consists of a single-channel terminal in which the
available band is used for data transmission (D-type channel). In the case of the 40 W
model, for example, the simplest version is the RFL 9506-40D terminal.
Version D constitutes the basic equipment for each model and can be transformed into any
of the other versions of the same model by the simple addition of the corresponding
modules in each case.
The speech-plus terminal (version T) is obtained by including a speech module in the basic
equipment. If on the other hand the two modules necessary for a second channel are
added, the twin-channel terminal is obtained, which permits two data channels to be
established (version DD). The terminals with a speech-plus channel and a data channel
(version TD) and with two speech-plus channels (version TT) are respectively obtained by
adding one or two speech modules to the DD version.

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The different models and their corresponding versions are indicated in Table 1.
SINGLE CHANNEL TWIN CHANNEL
DTDD TD TT
5W RFL 9506-05D RFL 9506-05T RFL 9506-05DD RFL 9506-05TD RFL 9506-05TT
20 W RFL 9506-20D RFL 9506-20T RFL 9506-20DD RFL 9506-20TD RFL 9506-20TT
40 W RFL 9506-40D RFL 9506-40T RFL 9506-40DD RFL 9506-40TD RFL 9506-40TT
80 W RFL 9506-80D RFL 9506-80T RFL 9506-80DD RFL 9506-80TD RFL 9506-80TT
DData transmission channel
TSpeech-plus transmission channel
Table 1Designation of the different RFL 9506 terminals
1.2 OPTIONAL SERVICES
RFL 9506 terminals have two types of optional modules; one type permits the facilities of
the terminal to be extended while the other type allows other equipment to be incorporated
in the same terminal.
The number of options that can be included in each terminal depends on the quantity and
type of channels that it has. The number of options can be chosen from among six in a
D-type single-channel terminal and two in a TT-type twin-channel terminal.
The different options for the speech module are the following:
−4-wire or 2-wire exchange-side telephone termination.
−2-wire subscriber-side telephone termination.
−Party-line termination.
The optional modules that allow the facilities of the terminal to be extended are the
following:
−Fixed-band VFT-transit filter.
−Programmable amplitude and/or phase equalizer.
−Data input/output module.
The following is the optional equipment that can be incorporated in RFL 9506 terminals:
−Teleprotection terminal. Based on digital signal-processing, this terminal comprises
a teleprotection system. Its application is possible in teleprotection systems in which
use is made of blocking as well as direct or permissive tripping.

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2PARTICULARITIES OF THE SYSTEM
2.1 MODULATIONS AND DEMODULATIONS
On the transmit side, the RFL 9506 terminal carries out the transposition of each 4kHz
channel to a band of frequencies that extends from 40 kHz to 508 kHz. This transposition
is achieved by means of a triple frequency conversion. The base band can be situated at
any point within the carrier-frequency range with a resolution of 1Hz, which not only
permits the equipment to be adapted to any channelling of frequencies but also solves
special interference problems by means of the adequate displacement of the band.
The type of modulation used is single side-band with suppressed carrier. This makes
possible the best use of transmit power given that it is all used for user information.
Figure 1shows the transmission modulation plan for a twin-channel system. In the
single-channel system the modulation process is the same as that of channel 1 and is
represented in Figure 2. The following information describes the frequency-conversion
process carried out in transmission for a twin-channel system, to which is analogous the
process for a single-channel system.
The two first modulations are made at fixed frequencies and the third at a frequency
generated digitally in 1 Hz steps. The first is achieved at a frequency of 12 kHz for channel
1 and at 16 kHz for channel 2. A 12 kHz to 16 kHz band-pass filter in channel 1 and
another of 16 kHz to 20 kHz in channel 2 select the higher band. The pilot signal, centred
at 12150 Hz for channel 1 and at 16150 Hz for channel 2, is added to each channel. The
signals are subsequently mixed to obtain the first modulation intermediate frequency (IF)
band that extends from 12 kHz to 20 kHz. The second modulation is accomplished at
768 kHz or 800 kHz, according to whether the band to be transmitted is inverted or erect,
and in both cases, after filtering, a band of 780 kHz to 788 kHz is obtained. Finally the third
modulation, which transposes the band to the desired frequency of between 40 kHz and
508 kHz, is carried out at a programmable frequency, f
0, of between 828 kHz and
1288 kHz. This frequency is generated by the direct digital-synthesis (DDS) technique by
means of a numerically-controlled oscillator (NCO). The band of undesirable frequencies is
eliminated by a low-pass filter with a 508 kHz cutoff frequency.

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Figure 1Transmission modulation plan for a twin-channel system

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Figure 2Transmission modulation plan for a single-channel system

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The inverse transposition is carried out in reception and the channels occupy a basic
bandwidth of 4kHz or 8kHz according to whether the system is single or twin channel.
Figure 3shows the reception modulation plan for a twin-channel system. The following
information describes the frequency-conversion process carried out in reception for a
twin-channel system.
The first demodulation is carried out at a frequency generated digitally by the same
process as that indicated in transmission and the second and third demodulations are
achieved at fixed frequencies.
The high-frequency signal that enters the equipment is demodulated by means of a
selected frequency of between 700 kHz and 1160 kHz to obtain, after 652 kHz to 660 kHz
band-pass filtering, the first-demodulation frequency band. The second demodulation is
carried out at a frequency of 672 kHz or 640 kHz according to whether the high-frequency
band is inverted or not. Immediately after, the second-demodulation frequency band is
obtained, with a 16 kHz to 20 kHz band-pass filter for channel 1 and a 12 kHz to 16 kHz
band-pass filter for channel 2. The third demodulation is carried out at a different fixed
frequency in each channel, this being at 20 kHz for channel 1 and at 16 kHz for channel 2,
and, after filtering in the 4 kHz band, the signal is recovered in the base band.
The pilot tone for each channel is obtained from the band of second-demodulation
frequencies, where it is centred at 19850 Hz for channel 1 and at 15850 Hz for channel 2.
After crossing the AGC circuit, this band is demodulated by means of a 24 kHz carrier
frequency for channel 1 and a 20 kHz carrier frequency for channel 2. In both cases, and
by means of a narrow-band filter centred at 4150 Hz, the pilot signal is extracted for later
use.
In the single-channel system there are two different modulation plans in reception,
Figure 4a) and b), depending on the relative positions of the transmission band and the
reception band.
In the case of Figure 4a) the demodulation process is the same as that of channel 1 of a
twin-channel system.
In the case of Figure 4b) the second demodulation is carried out at a frequency of
676 kHz or 636 kHz, instead of 672 kHz or 640 kHz, according to whether the
high-frequency band is inverted or not. From this point on the process is analogous to
that represented in Figure 4a).
The purpose of these two modulation plans in reception for a single-channel system is to
leave the transmission band out of the pass band of the intermediate-frequency filter.

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Figure 3Reception modulation plan for a twin-channel system

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b) Second-demodulation frequencies of 676 kHz and 636 kHza) Second-demodulation frequencies of 672 kHz and 640 kHz
Figure 4Reception modulation plans for a single-channel system

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2.2 USE OF THE BASE BAND
The available band, extending from 300 Hz to 3850 Hz, can be used for the transmission
of data at high speed, various VF telegraph channels, teleprotection signals (D-type
channel) or for a speech-plus service (T-type channel). Table 2indicates the maximum
number of standardized channels of 50, 100 and 200 Bd that can be situated in the D-type
channel.
ITU-T Recommendation R.35 R.37 R.39 R.38A R.38B
Transmission rate (Bd) 50 100 100 200 200
Separation (Hz) 120 240 170 480 360
Number of channels 29 14 20 7 9
Table 2Maximum number of channels for a D-type channel
The number of higher-rate FSK channels that can be transmitted in the same band is three
for a transmission rate of 600 Bd (with a separation of 960 Hz) and two for a rate of
1200 Bd.
In the T-type channel, where the available band is shared between speech and data, the
speech band is limited by a frequency lower than 300 Hz and by an upper one that is
programmable between 2000 Hz and 3400 Hz. The superimposed band extends between
1.06 times the cutoff frequency selected for the speech band and 3850 Hz. The maximum
transmission rate that can be obtained in the superimposed band is 1200 Bd when the
speech band is limited to 2000 Hz.
2.3 USE OF THE PILOT CHANNEL
The pilot is situated below the available band, at the virtual frequency of 150 Hz, which
makes all of the band between 300 Hz and 3850 Hz available for the transmission of
information.
The following information describes the different functions performed by the pilot channel.
Automatic Gain Control (AGC)
The equipment supervises at all times and in an independent way the level of the pilot
signal received in each one of the channels. The amplitude of this signal, once digitized, is
used to carry out the automatic gain control of the receiver. Thanks to the use of digital

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processing techniques, it is also possible to compensate for a level variation of the receiver
outputs, which is caused by the presence of noise in the pilot channel.
Link synchronization
The synchronization of link terminals is based on a master-slave operation; the
configuration of the equipment as either a master or a slave is defined by program.
When the equipment is configured as a slave, the synchronization circuits compare the
received pilot-tone frequency with the frequency of a reference signal internally generated
by the main oscillator. As a result of this comparison, a control signal is generated that
governs the main oscillator, synchronizing in this way the link. The synchronization circuits
operate constantly as long as dialling impulses are not being transmitted through the pilot
channel; when internal information is being transmitted through the pilot channel, this
transmission is periodically interrupted, thereby allowing the link to continue being
synchronized.
In twin-channel equipment the synchronization is carried out from the pilot signal of
channel 1. If the user wishes to synchronize the link, single or twin channel, one of the
terminals must be configured as a master oscillator and the other as a slave. Figure 5
shows an example of the configuration of the oscillators of a twin-channel terminal linked
with two different single-channel terminals. In this case the twin-channel terminal must
always be configured as a master and the two single-channel terminals as slaves.
Figure 5Example of synchronism between a twin-channel terminal
and two single-channel terminals
Telephone signalling
Modulating the pilot signal by frequency shifting at a maximum rate of 50 Bd,
corresponding to 25 impulses a second, permits telephone signalling to be transmitted.

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Internal data transmission
The supervision of the system is carried out by transmitting data through the internal
communication channel at a rate of 50 Bd. The transmission is interrupted when telephone
signalling appears and is resumed when it has no transitions.
Furthermore, data transmission is periodically interrupted in order to carry out the link
synchronization.
Noise spectral density
The system estimates the noise spectral density from the measurement of the noise power
in the band of the pilot tone. Assuming that this density is constant in the whole 4kHz
channel, the signal-to-noise ratio is independently calculated for each of the channels.
The value thus determined is compared with pre-set thresholds in order to block the
previously-programmed audio-frequency outputs and to deliver an excess-noise alarm.

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3PROGRAMMING, CONFIGURATION AND SUPERVISION
OF THE SYSTEM
The RFL 9506 terminal can be fully programmed by using a PC connected to an RS-232C
interface; the corresponding information is stored in two different EEPROM circuits as a
precaution.
The programming can be carried out directly, from a PC connected to the terminal to be
programmed, or indirectly, by storing the information on a diskette for its subsequent
transfer to the terminal by using a PC. In the first case only those modules that are already
included in the terminal can be programmed, while in the second case any previously
defined configuration can be programmed.
Illustrations a) and b) of Figure 6show the two types of programming mentioned. Drawing
c) refers to a case where access to the network is gained by means of a modem for
supervision functions and in order to program from a distance.
The programming system is structured in four parts: the first controls the flow of
information that enters and leaves the RFL 9506 program, the second allows the RFL 9506
terminals to be configured and programmed, the third allows the terminal to be diagnosed
and the system to be supervised and the fourth contains a help menu for the
commissioning and maintenance of the equipment.
The programming is protected by password in order to impede the alteration of operating
parameters by unauthorized personnel.

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Figure 6Programming possibilities

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3.1 CONFIGURATION AND PROGRAMMING MENU
This menu allows the user to define the identification and configuration of the terminals, the
transmission frequencies, the input and output levels of the signals and their modulation
percentages, and the operating parameters of the optional modules. It also allows the
internal clock of the equipment to be set, alarms to be assigned to external-signalling
relays, the type of output blocking to be defined and so on.
Terminal identification
RFL 9506 terminals are distinguished by means of their serial number. There is also an
additional field where the user can add a suplementary description of up to 50 characters.
Because each of the terminals can be identified, the serial number is indispensable in
supervision and programming from a distance, and in order to assign to each of them the
corresponding programming when this has been stored on a diskette.
Terminal configuration
Before programming the operating parameters it is necessary to configure the terminal.
The output power (which can be of 5, 20, 40 or 80 W), the number of channels, their use
(speech-plus or data transmission) and the options incorporated in the equipment are
defined by means of this configuration. The operating mode of the equipment of a link, one
as a master and the other as a slave, must also be configured if the link terminals have to
be synchronized with each other.
Carrier-channel frequencies and bands
The carrier frequency of the desired channel is defined by introducing, from the
programming terminal, the values of the virtual carrier frequency, for transmission and
reception, and the type of band, which can be erect or inverted.
The only manual adjustment required is that of the transmission and reception line filters.
The program contains a help menu in which the operations for the adjustment of these
filters are indicated for each channel.
Modulation levels and percentages
The system allows the modulation percentages assigned to each signal as well as their
input and output levels to be defined. This section also defines the power boosting used to
send the teleprotection signal, as well as the signals that must be excluded when it is sent.

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Blocking and alarms
The audio-frequency outputs can be blocked because of pilot loss or excessive noise. The
user can for each output define the signal-to-noise ratio for which blocking must be
effected as well as the value of excess noise which causes the external alarm to be
activated.
All the alarms of one particular terminal, as well as those of the collateral terminal, are
displayed on the front plate of the power-supply module. This module contains four relays,
three with a simple contact and one with a double contact. To each of these relays can be
assigned, from the programming system, an alarm or combination of alarms for their
external signalling.
Optional modules
All parameters of the optional modules that can be programmed, such as the teleprotection
terminal characteristics, equalizer values and so on, are defined from the programming
terminal of the system.
If the equipment incorporates the speech module, the definition must be made of the upper
limit of the corresponding band of frequencies, the use or not of the dynamic
compressor-expander circuit and the configuration of the exchange-side telephone
termination, which can be of two or four wires.
3.2 SUPERVISION MENU
The supervision menu allows information to be gained about the state of each terminal of
the link. The corresponding process of compilation and presentation is automatic for some
data while other data have to be requested by the user.
The supervision of the remote terminal is carried out by transmitting data through the
internal communication channel, which can only take place when the channel is not used
for link synchronization and when there are no transitions in the signalling channel. If
signalling appears while data are being transmitted, this transmission process is
interrupted and resumed again once the sending of telephone signalling has finished.
The information provided by the supervision system that is related to each terminal is the
following:

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−Terminal alarms.
−Chronological list of alarms.
−Chronological list of events.
−Receive pilot level.
−S/N ratio.
Presentation of alarms and events
Ten local-terminal alarms and the same alarms for the remote terminal that are transmitted
automatically through the communication channel are displayed on the front plate of the
power-supply and alarms module. These alarms are:
−Power-supply failure.
−Output amplifier failure.
−Excessive receive level.
−Loss of synchronism.
−Frequency-synthesizer failure.
−Pilot loss in channel 1.
−Pilot loss in channel 2.
−Low S/N ratio in channel 1.
−Low S/N ratio in channel 2.
−Card out.
The appearance and disappearance of these alarms is stored in a register together with
the indication of the date on which and time at which they were produced.
Events related to the link service, such as the activation of teleprotection, the switching on
of the terminal, the modification of the programming and insertion of the telephone handset
in the terminal are also introduced in the same register. The register has a maximum
capacity of one hundred alarms and events; when the limit is reached the events or alarms
introduced at the beginning of the register are eliminated.
State of the system
From the supervision menu it is possible to consult, from each end of the link, the
parameters programmed in the terminal and the data concerning its present state, such as

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the level of the receive pilot, the chronological list of alarms and events and the data
regarding the estimated value of the spectral density of the noise. Starting from these data
it is possible to calculate in the programming terminal the signal-to-noise ratio for different
bandwidths, corresponding to different speech as well as data channels.
3.3 COMMISSIONING HELP MENU
The help menu is provided to facilitate commissioning and alignment operations and
system maintenance. The menu contains the procedures for carrying out line-filter
adjustments and instructions for making the loops necessary to check the functioning of
the link and some tables showing the configuration of the switches of the equipment as a
function of the number of channels and of whether the transmit and receive bands are
adjacent or non-adjacent.
Line-filter adjustment
For each transmission channel the help menu indicates the jumpers to be made for the
programming of the central frequency of the line filters in transmission and reception as
well as the adjustment of inductances for the setting of the bandwidth of these filters. This
adjustment is carried out by means of a signal generated by the RFL 9506 terminal's own
transmitter.
Control of audio-frequency loops
To control the state of a communication system it is necessary to know the response curve
of each link. The supervision menu allows the user to obtain this information from one end
of the link by establishing two types of loops at the other end. The first, which has
signal-level regeneration at said end, enables the response curve of the return circuit to be
made known. This is possible thanks to the measurement of the received signal, for which
it is known that the transmission level is constant. The second loop, which does not have
signal-level regeneration, allows the response curve of the looped circuit to be obtained
and, therefore, allows the response curve of the outward circuit to be calculated. The
response curves are obtained by carrying out a channel sweep by means of an external
generator.
The help menu indicates how to carry out the operations mentioned.