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Radio HSA Thales RT-3600 → RT-4600 →
Radio Remote Control Set
KL/GRA-3686 is a remote control set for a number of military HF/VHF radio
sets of Philips,
HSA, Thomson
and Thales,
developed around 1987 by
Hollandse Signaalapparaten (HSA) 2
in Huizen (Netherlands).
The set consists of two units — a local device and a remote one —
and was initially developed for the RT-3600
and RT-4600 radios
– in which case it replaced the earlier KL/GRA-6 remote control set –
although additional versions were available for other radios,
such as SPIDER.
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The set consists of two similar boxes that allow two
radios to be controlled
via a regular 2-wire line (WD-1/TT) that can be extended up to 3 km.
One box – the Local Control Box (LCB) –
is fitted close to the radio, whilst the Remote Control Box (RCB)
is placed at the other end of the field line.
The image on the right shows the two boxes. At the left is the
LCB which has two fixed cables for connection to one or two
radios. At the right is the RCB, with an H-5050 handset
connected.
A second H-5050 handset can be connected to the LCB for
direct communication with the RCB.
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The devices are powered by three common D-size dry battery cells of 1.5V each,
that are held in a cylindrical battery compartment that can be accessed
via a large circular screw-cap at the side.
Up to two radio sets can be controlled in simplex or duplex mode,
from the Remote Control Box (RCB) as well as from the
Local Control Box (LCB).
The standard version of the KL/GRA-3686, also known as the A-version,
was intended for use with the Philips
RT-3600 and RT-4600 radios.
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The diagram below shows a typical setup of the KL/GRA-3686. At the left
is the C-3686A Local Control Box (LCB), which can be connected to
one or two 3600/4600 radios.
In case of stand-alone use, a handset can be connected
directly to this unit. In all other cases, a standard 2-wire field telephone
line (WD-1/TT) is connected to the two terminals at the right of the
front panel.
At the other end, the 2-wire line is connected to the terminals at the
left of the front panel of the C-3686 Remote Control Box (RCB).
A standard H-6060 handset 1
can be connected to either of the two control boxes, and a
MODE selector allows any combination of the two connected radios for RX and TX,
allowing single-channel (simplex) or split-frequency (half-duplex) operation
[A].
A direct call between the LCB and RCB is possible, by placing the MODE
selector in the TEL position and pressing the red CALL-button at the top right.
This will ring the buzzer at the other end.
The LCB can also be used on its own, as a local radio remote control unit,
for example when used inside a vehicle. In that case, the distance between the
LCB and the radio is limited by the length of the 10-way cable. In addition,
it allows half-duplex operation by adding an second radio.
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The diagram below shows the front panel of the Remote Control Box (RCB).
At the left are the terminals for the 2-wire field telephone line. To the right
of the lower terminal is the MODE-selector, which also acts as the
power switch. Directly above it, are the buzzer and the ringer volume knob,
which are used in case of a direct call from the Local Control Box (LCB).
At the right are the sockets for connection of the H-5050 handset
and the optional LS-166/U speaker. There are three red LED
indicators on the front panel: for battery level, radio 1 transmission and
radio 2 transmission, each of which can be covered by a pivoting flap. At
the right side is a large screw-cap behind which the three 1.5V D-size
batteries are installed.
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OFF Power off BATT Check battery voltage level (uses the optical indicator) TEL Direct call to the RCB (telephone) TX1/RX1 Simplex on radio 1 TX1/RX1+RX2 Transmit on radio 1, receive both radios TX2/RX1+RX2 Transmit on radio 2, receive both radios TX2/RX2 Simplex on radio 2
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In the case of the SPIDER-variant — the KL-GRA-63686(S) — a handset with
an old-type 10-pin plug was used, as the
5-pin U-229 sockets
on the front panels were replaced by a 10-pin U-79/U sockets.
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The suffix 'S' is uncertain, as the name tag of the
Spider-version of the KL/GRA-3686
in our collection appears to be missing.
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Remote Control Box (RCB)
C-3686
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The Remote Control Box (RCB) is used at the far end of a 2-wire
field telphone line that can be up to 3 km long. It has sockets
for a HC-5050 handset and for a speaker,
and is powered by three internal 1.5V D-size batteries.
The device can control up to two radio sets, in simplex and duplex
mode. It can also be used for direct communication with the
Local Control Box (LCB) without accessing the radio.
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Local Control Box (LCB)
C-3686A
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The Local Control Box (LCB) is the interface from one or
two radio sets, to a 2-wire field telephone line that can
be up to 3 km long. It can also be used for direct communication
with the Remote Control Box (RCB).
At the left are two fixed cables 1 that should be connected
to the audio in/out sockets of the radio(s).
Depending on the
version, different connectors may be present at the far end of
these cables. The standard version of the LCB (C-3686-A) is
wired for the RT-3600
and RT-4600 radios.
The device shown here is a C-3686-B, which is
wired for a different radio.
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Each KL-GRA-3686 set came with two identical HC-5050 handsets,
one of which should be connected to the LCB, and one to the RCB.
Note that these handsets have a dynamic microphone element, and are
exclusively supplied for this set. They can not be replaced by handsets
with a carbon type microphone.
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A standard LS-166/U speaker can be connected to the 10-pin U-79/U socket
at the front panel of the Remote Control Box (RCB). This was
the standard speaker for European and American military radio
sets in the 1970s and 80s.
The LS-166/U speaker is currently missing from our collection.
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Instruction Card
IK-11-473
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The set came with a yellow folded instruction card IK-11-473,
in the Dutch language. It explains how to connect the two units
and how to operate them in the field.
The card was made specificially for use with the C-3686-A
in combination with the
RT-3600 or RT-4600
radio, but is also applicable to other versions of the KL-GRA-3686.
➤ Download instruction card
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The interior of the device(s) can be accessed by loosening the four large
bolts in the corners of the front panels, and sliding off the rear case
shells. Note that the case shell holds the battery compartment which is fitted
to the main unit by means of a fixed 2-wire (red/black) connection.
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The image on the right shows the interior of the C-3686A Local Control Box
(LCB). The electronic circuits are divided over two PCBs that are both
fitted to the rear of the front panel. These PCBs hold the electronics
for the audio amplifiers and the digitally encoded signal for the 2-wire
line.
Three small PCBs with filtering components are fitted close to each of the
sockets. Furthermore, a special filtering PCB is mounted directly to the
terminals of the 2-wire interface. It also holds a line transformer,
which is similar to the transformer of a common (analogue)
telephone set.
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The device is powered by three D-size dry battery cells that should
be installed in the cylindrical battery holder that is mounted at
the centre of the case shell. It is clearly visible in the image above.
To save batteries, the MODE selector should be set to OFF when the
device is not used.
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© Crypto Museum. Created: Saturday 21 November 2020. Last changed: Thursday, 05 May 2022 - 06:23 CET.
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