Acom 600S Operating Manual
HF + 6 m LINEAR AMPLIFIER
OPERATING MANUAL
ACOM 600S
HF + 6 m SOLID STATE LINEAR AMPLIFIER
OPERATING MANUAL
1. GENERAL INFORMATION....................................................................................................................... 2
1-1. Inroduction and description .................................................................................................... . 2
1-2. Owner assistance ................................................................................................................... 2
1-3. Equipment supplied and options ............................................................................................. 2
1-4. Features ................................................................................................................................. 2
1-5. Safety considerations, explicit definitions ................................................................................ 3
2. INSTALLATION ........................................................................................................................................ 4
2-1. Unpacking and Initial Inspection ............................................................................................. 4
2-2. Amplifier location selection; cooling. ....................................................................................... 4
2-3. Connecting the amplifier within the shack ............................................................................... 5
2-4. Installing options and connecting to external devices (transceiver, computer etc) .................. 7
3. INITIAL POWER ON AND SETTING INTO OPERATION ........................................................................ 9
3-1. Low-energy (waiting) mode of the power supply ..................................................................... 9
3-2. Front panel - controls and indication ....................................................................................... 9
3-3. Initial turning on – activation of the main power supply ......................................................... 10
3-4. Basic screen ......................................................................................................................... 10
3-5. Control system – buttons and menus .................................................................................... 12
3-6. Test transmission .................................................................................................................. 12
4. OPERATION WITH THE AMPLIFIER ...................................... ............................................................... 16
4-1. Change of modes RX / TX and Operate / Stand-by; option AUTO OPERATE ...................... 16
4-2. Band change, standard and expanded frequency coverage ................................................. 17
4-3. Change of antennas and operation with an external antenna tuner ...................................... 18
4-4. Cooling and fans operation; modes with increased heat loading ........................................... 18
4-5. Monitoring the amplifier operating regime ............................................................................. 18
4-6. Automatic protection system ................................................................................................. 18
5. MENUS – USEFUL INSTRUMENTS AND OPTIONS............................................................................. 20
5-1. Menu “Measurements in the amplifier” – AMP MEASURE .................................................... 21
5-2. Menu “Service functions in the amplifier” – AMP SERVICE. ................................................. 21
5-3. Menu “Selection of CAT/AUX interface” – CAT/AUX SETTINGS .......................................... 22
5-4. Menu “USER PREFERENCES” ............................................................................................ 23
5-5. Reading the FAULTS LOG ................................................................................................... 24
5-6. Menu "RESTORE DEFAULT SETTINGS" ............................................................................ 25
6. REMOTE MONITORING AND CONTROL ............................................................................................. 26
6-1. General information .............................................................................................................. 26
6-2. Commands set ...................................................................................................................... 26
7. MAINTENANCE ................................................................................................................................. .... 27
7-1. Periodic maintenance; general checks and cleaning ............................................................ 27
7-2. Replacement of fuses ........................................................................................................... 27
7-3. Simplified schematic diagram; theory of operation ................................................................ 28
7-4. Using the fault codes (signatures) for diagnostics ................................................................. 31
7-5. FIRMWARE UPDATES ........................................................................................................ 32
8. SPECIFICATIONS .................................................................................................................................. 32
8-1. Parameters ........................................................................................................................... 32
8-2. Functions .............................................................................................................................. 33
8-3. Storage and shipment ........................................................................................................... 33
9. DISCLAIMER of LIABILITY .................................................................................................................... 33
CONTENTS
Page 1 of 33
1. GENERAL INFORMATION
1-1. Inroduction and description
This manual describes the installation, operation, and maintenance of the HF+6m solid-state linear power
amplifier ACOM 600S.
ACOM 600S is a state-of-the art linear amplifier which covers all amateur bands from 1.8 through 54MHz and
provides more than 600 W output power (PEP or continuous carrier) with less than 30W of drive. The working
parameters of the amplifier are indicated on a multi-functional, high resolution color display. The amplifier control
is performed with only six buttons from the front panel, directly by CAT interface from the transceiver or remotely
– by RS232 interface.
1-2. Owner assistance
If technical or operating assistance is needed, please contact your local dealer first. In the unlikely event you
need further information, you may get in touch with ACOM as follows: fax: + 359 2 920 96 56, telephone +359
2 920 96 55, e-mail: acom@acom-bg.com, acom@mail.orbitel.bg or by mail to: blvd. Nikola Mushanov 151, 1330
Sofia, Bulgaria. The ACOM Internet page is: www.acom-bg.com.
1-3. Equipment supplied and options
The amplifier is supplied in single box, which includes:
- the amplifier ACOM 600S;
- this manual with a CE declaration of compliance;
- four pieces of spare fuses;
Directly from ACOM or from your dealer you can also buy some of the following options:
- CAT interface cables for connecting the supported transceiver models (please specify the wanted one);
- Technical compact disk (CD), containing complete schematic diagrams, graphic information and parts
layouts of the printed circuit boards, as well as a list of commands set and the rules for remote control of
the ACOM 600S amplifier.
1-4. Features
5" (108x65mm) high resolution color display, 800x480 pixels, and 24-bits colors.
The final stage uses field effect (MOSFET) transistors type MRFE6VP6300H, which, according to their
manufacturer - Freescale Semiconductor - are designed to withstand high mismatch (SWR) at the output
and are intended for operation in aerospace, industrial, mobile, and radio broadcast applications.
Compatible with all transceiver models available on the market - does not need any special signals:
"ground on transmit" (PTT) and 30W of RF drive power is sufficient.
Broadband input circuit providing a perfect transceiver load with SWR below 1.2:1 (typically 1.1:1),
without retuning throughout the whole frequency range from 1.8 to 54MHz.
The overall operation of ACOM 600S is extremely simplified: the screen menus are intuitive and easy to
follow and no special skill is required from the operator when changing frequency bands.
Possibility of automatic control – when connected to a transceiver with a CAT interface, the amplifier
monitors constantly, duly follows the operating frequency, and changes the bands accordingly.
Even if not connected with CAT interface, the amplifier monitors the frequency of the input signal through
the built-in frequency counter and automatically switches over the bands.
Page 2 of 33
Remotely controlled by RS232 interface.
Takes care of itself during operation due to the continuously working protection circuits in all modes.
The operator can monitor digitally more than 10 parameters concerning the working regime of the
amplifier.
Easy maintenance – detailed data (55 parameters) about each of the last 28 hard-fault protection trips is
stored in the amplifier’s nonvolatile memory.
Convenient for expeditions and field operation: extremely compact and light construction, extended
mains voltage range (85-132VAC and 170-265VAC through changing only the main fuses - no internal
switching), limited inrush current and purely sinusoidal consumed mains current, automatic Power Factor
Correction (PFC) – all significant parameters in operation from unstable mains, generators etc. features
achieved thanks to the built-in switching-mode power supply (SMPS).
Perfect electromagnetic compatibility (EMC) both with the highly sensitive as well as with the powerful
appliances in the radio station (receivers, computers, more amplifiers) exceeding the standard EMC
requirements due to the use of PFC and the built-in additional radio-frequency filters.
1-5. Safety considerations, explicit definitions
The linear amplifier ACOM 600S is apparatus Class I of protection against electric shock, i.e. the third grounding
lead of its mains cord (colored yellow with two green stripes) and the grounding stud on the rear panel, marked
GND (Fig. 2-1), must be connected to the grounding system of the shack for safe operation.
The ACOM 600S amplifier is designed to meet international safety standards and complies with CE safety and
electromagnetic compatibility requirements, as well as FCC regulations.
This operating manual contains an assortment of precautions, indications for cautions, and warnings that MUST
BE FOLLOWED by the user to ensure safe operation and always maintain the ACOM 600S amplifier in a safe
working condition.
PRECAUTIONS:
The EXPLICIT DEFINITIONS described below apply to this operating manual:
W A R N I N G notes call attention to a procedure which, if not correctly performed, could
result in personal injury, fire hazard or electric shock or lightning.
C A U T I O N notes call attention to a procedure which, if not correctly performed, could result in
equipment damage, not only in the ACOM 600S amplifier.
N O T E notes call attention to a procedure which, if not correctly performed, could result in
inconvenience.
W A R N I N G HIGH VOLTAGE!
The mains power voltage plus a high DC voltage up to 500V inside the
ACOM 600S amplifier are LETHAL! For your safety, pull the amplifier
power plug out of the mains wall outlet and WAIT AT LEAST three
minutes EACH TIME BEFORE you remove the cover of the amplifier.
W A R N I N G HIGH VOLTAGE!
NEVER ALLOW, ESPECIALLY CHILDREN, to push anything into holes
in the case - this will cause ELECTRIC SHOCK! Never touch an
antenna or antenna isolators during transmission or tuning - this may
result in an electric shock or burn. Never expose the amplifier to rain,
snow or any liquids. Avoid placing the amplifier in excessively dusty
environments or in direct sunlight. DO NOT OBSTRUCT COOLING
AIR movement areas.
W A R N I N G
Page 3 of 33
Do not undertake your own repairs or changes in hardware or
firmware of your ACOM 600S amplifier. Doing so will endanger your
or others' health or life or damage the amplifier and the equipment
connected to it. Such repairs or changes are not covered by warranty
and may void the warranty. The manufacturer is not liable for any
such repairs or changes. Any such repairs or changes are strictly the
responsibility of the person or persons engaging therein.
C A U T I O N
To avoid damage (not covered by the warranty) please read the
INSTALLATION - Section 2 of this operating manual carefully. If you have
any doubts or questions regarding the installation, operation or safety of
the ACOM 600S amplifier, please consult your dealer immediately.
2. INSTALLATION
2-1. Unpacking and Initial Inspection
C A U T I O N
Before you start any work on installing the ACOM 600S amplifier, please
thoroughly read through this manual. First carefully inspect the shipped
carton and Its contents as described below for anything missing from the
set (S. 1-3) or mechanical damages. If anything is missing or is obviously
damaged (scratched, bent, smashed or something is rattling inside or
moving freely when turning over, notify immediately your dealer! The
delay may Infringe the warranty conditions of the carrier.
N O T E
Keep the original packing for possible future transportation.
Take out and inspect carefully the contents of the cardboard carton for possible transportation damages. On the
amplifier check the chassis, the front panel, the display and the buttons below it and on the rear panel – all
connectors, the main power switch, the fuses, and the integrity of the power cable - especially at the area where
it comes out from the panel.
Check in the same way the options if such have been ordered.
2-2. Amplifier location selection; cooling.
Locate the amplifier close to the place where it will be used. You will need an easy access to the rear panel for
connecting cables, and of course, to the buttons and the screen on the front panel of the amplifier.
The ACOM 600S operates with forced air cooling. Locate the amplifier so that there are no objects or devices
closer than 10cm (4”). At an ambient temperature of 40ºC (104ºF) the exhaust air can reach 65ºC (150ºF), this is
why if nearby items are sensitive to heating from outside or use forced air cooling, increase the distances
accordingly.
C A U T I O N
Do not leave free papers, cloth or other light materials around and under
the amplifier. They may be drawn in by the cooling air stream and block
some ventilation apertures. Thus the amplifier will get easily and frequently
overheated which may age prematurely the materials in its construction
and lead to damages, not covered by the warranty.
Page 4 of 33
2-3. Connecting the amplifier within the shack
W A R N I N G
Before you connect the amplifier to external grounding, you should
advise with a licensed electrician and check-up whether such kind of
connection is allowed by the national and local electrical code, safety
rules, and regulations in force. Simultaneous connection to the earth
grounding and bonding may be inadmissible or may fall under special
requirements in some countries!
W A R N I N G
Never use the gas installation tubing as grounding. This can cause an
EXPLOSION!
W A R N I N G
Do not use the steam-heating or water-supply network tubing as
grounding! Thus, you may involuntarily expose to dangerous voltage
not only yourself but also other people using the same installation.
C A U T I O N
Have in mind that the grounding installation will have to withstand
emergency currents above 15A with minimal voltage drop on it thus it may
be necessary to improve its conductivity using heavier leads and lowerresistive grounding path. The grounding lead should be at least 4mm
(AWG 11 or SWG 13).
For details and recommendation on the grounding and RF counterpoise system concerning the electromagnetic
compatibility see also S. 3-6(g).
a) GND stud - external grounding connection of the amplifier. After having made strictly all check-ups
described above, first connect the grounding stud of the amplifier (located on the rear panel and marked
GND – Fig. 2-1) to the grounding system of the shack.
b) KEY-IN jack - amplifier input for receive/transmit control from the transceiver.
The transceiver switches the amplifier from receive mode into transmit mode (RX/TX) via grounding of the KEYIN input.
Connect a shielded cable from the respective control output of your transceiver, providing “ground on transmit”
(PTT), to the KEY-IN input on the amplifier rear panel (RCA PHONO jack socket – Fig. 2-1). Use a standard
“RCA PHONO” jack plug for connection to the amplifier.
The manufacturers of transceivers give different names to this output, for example: TX-GND, SEND, T/R LINE,
RELAY, PTT, and others. At some transceivers “ground on transmit” output should be activated by a software
command, a menu or via changing a switch on the rear panel or inside the transceiver. See instructions in the
manual of your transceiver.
C A U T I O N
Before connecting the KEY-IN input verify the electrical specifications of
the transceiver control output (from its own manual) to make sure of their
compatability. The signal voltage applied by the amplifier KEY-IN jack to
the transceiver control output “ground on transmit” does not exceed +12.6V
against ground and its closed-circuit current is below 6mA. See also S. 82(a).
N O T E
Your amplifier will not work if the KEY-IN input is not connected correctly. If
you experience any difficulty consult your dealer.
2
Page 5 of 33
Fig. 2-1 Rear panel connections
c) KEY-OUT jack - transmit-enabling control output from amplifier to the transceiver.
The KEY-OUT jack on the rear panel provides an additional control signal from amplifier toward transceiver. It
can be used for improving reliability of the receive/transmit (RX/TX) switching.
When the amplifier is not powered up, KEY-OUT is connected internally to KEY-IN through the contacts of a
relay inside the amplifier, thus always enabling transceiver transmission. Also, in Stand-by mode KEY OUT
unconditionally follows the state of the KEY-IN input. When in Operate mode however, KEY-OUT follows KEY- IN
only when all conditions for safe transmission have been found OK by the amplifier control circuit. At detection of
any risk, transmission is quickly disabled by means of opening the KEY-OUT circuit constrainedly.
C A U T I O N
KEY-OUT is a low-powered output, this is why make sure that the signal
voltage coming to it from the respective transceiver connection does not
exceed 50VDC (open circuit) and that its closed-circuit current is below
20mA.
If your transceiver has a suitable input, which disables transmission unless it is grounded externally, we
recommend that you connect it to the KEY-OUT jack of the amplifier. Use shielded cable terminated with а
standard “RCA PHONO” jack plug.
The manufacturers of transceivers give different names to this transceiver input, for example: TX-INHIBIT,
MUTE, LINEAR, and others. Check the manual of your transceiver. Approach your dealer for details. If your
transceiver has no such input, do not worry – ACOM 600S will operate normally without it as well – then KEYOUT jack can remain not connected.
d) RF INPUT – should be connected to the antenna input/output of the transceiver.
Connect a 50-Ohm coaxial cable with a connector type PL-259 from the transceiver output (antenna jack) to the
RF INPUT jack on the rear panel of the amplifier.
N O T E
When operating with the amplifier, do not turn on the transceiver built-in
antenna tuner (if present).
e) RF OUTPUT – should be connected to the antenna, antenna switch or tuner.
Connect a 50-Ohm coaxial cable with a connector type PL-259 from RF OUTPUT on the rear amplifier panel to
the antenna switch, tuner or antenna intended for the respective frequency band.
Page 6 of 33
C A U T I O N
If you use an amplifier for the first time in your shack, pay serious attention
to the size of coaxial cable from your amplifier output to the antenna. The
cable must be capable of handling the increased power safely, particularly
on the 10m and 6 m bands. This warning refers equally to the antenna
switch, tuner, and the whole antenna system, for example, for multi-band
antennas with resonance circuits (traps etc).
We recommend that you use coaxial cable sized as a minimum similarly to the following types: RG8x, RG8MINI,
RK50-4-11, RK50-4-13 or better still - RG213 or RK50-7-11. Consult your local supplier of coaxial cables to make
the right choice.
f) Preparation of the mains outlet for the amplifier, requirements for the installation and the mains
voltage.
C A U T I O N
Before connecting your amplifier to the mains, check-up with a licensed
electrician if it is properly wired and if your mains is adequate for the
current which the amplifier can consume at an emergency (up to10A from
200/240VAC mains and up to 15A from 100/120VAC mains). Also, make
sure that the grounding lead is connected properly in the wall mains outlet
intended for the amplifier. If subsequently you connect the amplifier to a
different outlet, make sure about it as well.
It is preferable for the amplifier to use the closest mains outlet. Make sure that the respective fuses, the voltage,
and the frequency of your power mains match the ACOM 600S amplifier specifications (see S. 8-1(g)).
g) Mains cord – installation of mains plug and main fuses suitable for your nominal mains voltage.
C A U T I O N
If your amplifier has only one mounted mains fuse (Fig. 2-1 / S. 7-2), it is
suitable ONLY for power mains networks of the type 0-220/240VAC, which
are standard in the EU.
C A U T I O N
Make sure you check whether the main fuses installed in your amplifier
correspond to your mains nominal voltage and if necessary replace them
as described in Section 7-2!
Because of differences among standards in the different countries, the mains plug is supplied and mounted by
your dealer. He connects a standard mains plug for apparatus Class I of protection against electric shock
corresponding to the national and local electrical code, safety rules, and regulations in force in your country.
C A U T I O N
The lead colored in yellow with two green stripes in the mains cord is the
grounding, while the blue and brown leads are active. When the amplifier is
only fitted with one mains fuse, then the fuse is connected in series with
the brown lead, which must be the actve.
If you have any doubt if the mains-cord leads are connected correctly in your mains plug, please consult your
dealer immediately. Using a licensed electrician, the user must implement the checks mentioned above each
time the amplifier is to be connected to a mains network outside the country in which it was purchased.
2-4. Installing options and connecting to external devices (transceiver, computer
etc)
a) CAT/AUX interface - connecting and operation with various transceiver models (see table 2-1 below and
the respective menu in S. 5-3 and Fig. 5-3).
Most of the modern transceivers that provide output data of their working frequency by a serial or parallel port or
as an analogue signal (0 to 8V depending on the frequency) can be connected to the CAT/AUX interface
Page 7 of 33
connector of ACOM 600S. This will allow the amplifier to follow the changes of the frequency bands automatically
and without any transmission, while the operator is operating with the transceiver.
For control of the amplifier through the CAT/AUX interface you need a special cable between the transceiver and
CAT/AUX connector (type HD-15) on the rear panel of the amplifier – Fig. 2-1. Such a cable can be supplied as
an option along with the amplifier or you can buy it from your dealer additionally, but you can assemble it yourself
as well, using information from table 2-1 and your transceiver's manual.
Schematics of cables for connecting to many transceiver models are readily available in the Technical compact
disk (CD) – an option to the amplifier, as well as on the ACOM Internet page (S. 1-2).
Table 2-1 shows the signals and the pin out of the CAT/AUX connector - rear panel of the amplifier.
Table 2-1
CAT/AUX
interface
PIN
PIN NAME DESCRIPTION SPECIFICATIONS
NO.
1 RxD Received Data TTL input
2 RxD Received Data RS232 input
3 TxD Transmitted Data RS232 output
4 TxD Transmitted Data TTL output
5 GND Ground 0 Volt
6 BAND
Analogue input 0 to +8V
voltage
7 B. data 0 Bit 0 TTL input
8 B. data 1 Bit 1 TTL input
9 B. data 2 Bit 2 TTL input
10 B. data 3 Bit 3 TTL input
Rear panel
view
11 ON RMT Remote Pwr On +4.5 to +15V / 3mAmax
1 to 2 seconds pulse
12 Debug
mode
CPU only Power
Input
+8 to + 15V / 0.4A
13 KEY-IN Transmit Request Rx/Tx control input
Less than +12.6V
Less than 6mA
14 KEY-OUT Transmit Enable O.C. output, 0 to +50V
20mA maximum
15 GND Ground 0 Volt
N O T E
Due to the variety of existing CAT protocols for different transceivers, the
amplifier response may be different for some transceiver models, as
described below.
- Some older transceivers employ a rather slow protocol or send frequency data with a delay of several
seconds – then the amplifier response will be delayed respectively;
- In some cases, when the transceiver is powered on after the amplifier, you may need to press and hold
up for one second the button BAND of the amplifier, up or down (Fig. 3-2), to make the transceiver inform
the amplifier about its frequency; in other occasions, the transceiver transmits its frequency only on
changes and you may need to move slightly the main frequency dial knob or change it in another way in
order to announce it to the amplifier after an initial power turn on;
- in "split" operation, not all transceivers provide frequency data of VFO A and VFO B correctly; if your
receive and transmit frequencies fall in different frequency bands (Cross Band Operation) and the
amplifier unnecessarily switches between them at each transition receive/transmit (RX/TX), you may
deactivate the amplifier’s CAT/AUX interface control while operating "split" (S. 5-3 and Fig. 5-3).
Page 8 of 33
b) RS232 Interface. Table 2-2 shows signals and pin out of the RS232 connector on the rear panel of the
amplifier. Details about connecting and using the RS232 interface are given in the Technical compact
disk (CD) – option to the amplifier and / or in the respective control programs.
This connector can remain unconnected until you decide to use the amplifier with remote control.
RS 232
interface
PIN
NO.
PIN
NAME
Table 2-2
DESCRIPTION SPECIFICATIONS
1 - Not connected 2 TxD Transmitted Data RS232 level output
3 RxD Received Data RS232 level input
4 - Not connected 5 GND Ground 0 Volt
6 DSR Data Set Ready RS232 level input
7 - Not connected 8 CTS Clear To Send RS232 level input
9 - Not connected -
Rear panel
view
3. INITIAL POWER ON AND SETTING INTO OPERATION
C A U T I O N
Do not turn on the amplifier for at least two hours after it is unpacked and
installed in its operating position. Pay particular attention whenever the
amplifier is moved from a very cold place to a very warm one because
unseen condensation may develop and this could result in damage to the
high voltage circuits of the amplifier. Under these circumstanves, do not
turn on the amplifier for at least 4 hours. A similar effect could occur
following a rapid warming of the room, such as winter use of a powerful
electric heater.
After having mounted and connected the amplifier according to the instructions in Section 2 INSTALLATION and
have followed all requirements, check whether mains switch on the rear panel is in turned-off position – in Fig. 21 the rocker of the POWER ON switch must be protruding from the side of the “ON” inscription. Afterwards insert
the mains plug of the amplifier into the mains outlet prepared for it. For now the amplifier remains turned off.
3-1. Low-energy (waiting) mode of the power supply
Now you can put the mains switch on the rear panel in a turned-on position, pushing its rocker so that it sinks
from the side of the “ON” inscription (Fig. 2-1). This will activate only the low-energy (waiting) mode of the power
supply and will illuminate the red LED above button ON/OFF on the front panel, while the main power supply is
still inactive and the display is dark.
3-2. Front panel - controls and indication
a) ON/OFF button – serves for manual (local) start up of the power supply from low-energy (waiting) mode
of the power supply (S. 3-1) into working mode, i.e. for activating of the main power supply and starting
operation with the amplifier. The same button is used also for main power supply deactivation – return
into the low-energy (waiting) mode of the power supply at ceasing operation with amplifier.
b) LED indicator above the ON/FF button. The red LED indicator glowing above the ON/OFF button at a
dark display shows that mains voltage is fed from the plug, the POWER ON switch on the rear panel
(Fig 2-1) is in a turned-on position, but the power supply is in its low-energy (waiting) mode (S. 3-1). In
this mode activation of the main power supply is expected to start operation with the amplifier.
Page 9 of 33
Fig. 3-1 Front panel
During operation with the amplifier the display is illuminated and the red LED above the ON/OFF button indicates
the button location which can be very useful in case of fast switching off in poor light conditions.
c) Keyboard with 6 buttons for manual (local) control of the amplifier. The function of each button is
prompted on the display above it. Depending on the menu displayed, the buttons may have different
functions.
d) The color display shows all the relevant information about the status of the amplifier.
3-3. Initial turning on – activation of the main power supply
In order to activate the main power supply at starting amplifier operation, press and hold on the ON/OFF button
on the front panel for one or two seconds - аbout three seconds later the display will flash and show the basic
screen showing the amplifier status and operation - Fig. 3-2.
After turning on, the amplifier stands in Stand-by or Operate mode – it depends on whether the AUTO OPERATE
option has been activated – see S. 5-4 USER PREFERENCES.
3-4. Basic screen
There are 9 information areas on the basic screen as follows:
a) Information area for the frequency band – the borders of the currently selected BAND are displayed.
If at start up of the amplifier there is no information about the operating frequency (neither the CAT/AUX nor the
RS232 interface is connected) the last working frequency is taken, which has been stored in the nonvolatile
memory of the amplifier.
Page 10 of 33
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