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Remote Control Set for SPIDER

KL/GRA-3686(S) 1 is a remote control set for the SPIDER VHF military radio, developed around 1987 by Hollandse Signaalapparaten (HSA) 2 in Huizen (Netherlands). The set consists of two units – a local and a remote device – and is in fact a modified version of the KL/GRA-3686 that was used with the RT-4600 and, to a lesser extent, with the earlier RT-3600 military radio sets.

The set consists of two similar boxes that allow the SPIDER 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 Local Control Box C-3686A, which can be connected to one or two SPIDER radios via the 10-pin sockets at the left. A standard handset can be connected to the 10-pin socket at the right. At the far right are the terminals for connection of the 2-wire line.
One half (radio end) of the Remote Control Set

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 terminator at the left. It is believed that, given the small number of SPIDER radios that were manufactured, only a few KL/GRA-3686(S) sets were made for the evaluation stage of the radio. The device shown above carries the internal HSA designator 9556 304 05300. The same designator was used for the regular version of the set, which suggests that it was an interim (engineering evaluation) solution.

  1. As the official designator is currently unknown, we have added the suffix '(S)' to identify the SPIDER-variant.
  2. HSA Huizen – informally known as SIGNAAL or SIGNAL – was formerly known as Philips Telecommunicatie Industrie (PTI). It was taken over in 1990 by Thomson, which has since been renamed Thales.

One half (radio end) of the Remote Control Set Front panel Interior SPIDER radio cable
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One half (radio end) of the Remote Control Set
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Front panel
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SPIDER radio cable

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 SPIDER radio sets. 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 SPIDER remote control unit, for example when used inside a vehicle. In that case, the distance between the LCB and the SPIDER is limited by the length of the 10-way cable. In addition, it allows half-duplex operation by adding an extra radio.

  1. 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 sockets.

All controls and connections of the C-3686A LCB and the C-3686 RCB, are located the front panels of the two devices. The diagram below gives an overview of the controls and connections on the body of the local control box. At the left are the 10-pin sockets for connection of one or two SPIDER radio sets. Note that this is different from the standard C-3686A, which has a fixed cable with a 5-pin U-229 connector at the end at these positions. The A/B selector between the two radio sockets is not used. On a standard C-3686A it is used to select the required radio type.

C-3686A(S) Local Control Box (LCB) - modified for SPIDER radio

At the right are the two spring-loaded terminals for connection of the 2-wire field line, at the end of which the C-3686 Remote Control Box (RCB) is connected. At the bottom right is the socket for a standard handset or a speaker. At the left is the MODE selector that also acts as POWER switch.

At the top are the signalling features, from right to left: a CALL button (to call the remote end), a buzzer (when called), a knob to set the buzzer volume and an optical indicator that is used when in SILENT mode. The indicator is shielded by a movable lid. It is also used as BATTERY indicator.

MODE selector
  • 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
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.

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.

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.

Interior Interior Quick glance at one of the PCBs Quick glance at the other PCB Top view Modifications Wiring to the radio sockets 2-wire interface transformer
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Quick glance at one of the PCBs
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Quick glance at the other PCB
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Top view
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Wiring to the radio sockets
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2-wire interface transformer

Compared to the regular version of the KL/GRA-3686, the following modifications are observed:

  • Fixed wiring for radio(s) replaced by 10-pin socket
  • 5-pin U229 socket for H-6060 handset replaced by old 10-pin socket
  • Various internal modifications
A complete (original) KL/TGA-3686 configuration, consists of the following items:

  • C-3686A
    Local Control Box (LCB)
  • C-3686
    Remote Control Box (RCB)
  • H-6060
    Handset (2x)
  • IK 11-473
    Instruction card
  • CY-3686
    Carrying bag
Optionally, the following can be added:

  • LS-166/U
Help required
At present, no further information about the KL/GRA-3686 or the (S)-variant is currently available. We are looking for operating instructions, circuit diagrams and/or any other documentation. We are also looking for a C-3686 Remote Control Unit (i.e. the part that is needed at the other end of the 2-wire line). If you can provide any of these, please contact us.

  1. Instructiekaart IK 11-473, Afstandsbedieningsuitrusting KL/GRA-3686
    Instruction card IK 11-473, remote control set KL-/GRA-3686 (Dutch).
    Royal Dutch Army, 8 January 1987. #CM303000
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Crypto Museum. Created: Tuesday 18 December 2018. Last changed: Thursday, 27 December 2018 - 11:58 CET.
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