Radiometrix Ltd

KDEC

page 2

General Description

KDEC is optimised for use with the KFX2 (Key-fob transmitter) or KTX2 modules by means of a jumper

link on the PCB, according to the preference of the user.

When optimised for KFX2 it is not possible to activate more than one output per transmission and up to 5

relay outputs are available, matching the number of button inputs on the KFX2.

Alternatively, when optimised for use with the KTX2 module, the KDEC has simple output functionality.

New function-codes are fed to the relays as they are received, e.g. reception of a function-code (S0, S2)

will activate relays 1 and 3 simultaneously. For both versions, momentary/latched relay action is also

selected by means of a jumper link on the board.

Visual Indications

The following status LEDs will light, depending on the status of KDEC.

LED

Function

Description

1 - 5

Relay active (Red)

Relay energised; S0-S3 Function-code output

LOW-BATT TX Low Battery (Red)

Transmitter supply voltage <3.8V (approx.)

LEARN

Learn/Learnt (Orange) Multi-function indicator – see below

POWER

POWER (Green)

Power supply present

Using KDEC

Learning a transmitter

The Learn button is pressed momentarily (<1s) and a 6-second (approx.) window follows, during which

the Learn LED is lit and a message received from a Radiometrix code-hopped transmitter during this

period is used to Learn that transmitter into the KDEC memory. The function code used to activate the

transmitter during learning is also stored in memory and when the same function code is used again

from that transmitter during normal operation the Learn LED lights to indicate this. Note: if a

transmitter has already been stored it is simply re-learned (with the function code updated if this is

different). Upon learning a transmitter the Learn LED flashes several times to indicate success.

Activating output relays

Once a transmitter has been learned its transmissions will be acted upon, i.e. the function code contained

within the transmission is fed to the output relays. When optimised for use with KFX2, extra processing

ensures that only one relay at a time is energised.

Either momentary or toggled/latching outputs can be used. Note that this distinction applies to all the

outputs, not individual relays. When Momentary Output mode is selected the output is activated for a

short period (470 – 570ms) for reception of a single message. If the same message is received repeatedly

the output status is refreshed during this period: in effect, the output is “held-on” whilst a user keeps the

relevant function line enabled at the transmitter. When Latched Output mode is selected the decoding of

a single message causes the function-code within the message to toggle the output(s).

Care should be exercised when using Latched (or more accurately ‘toggled’) mode with KDEC optimised

for use with KTX2; consider the following example: one function-line (S0) is taken high and held high at

the transmitter. On reception of the message, Relay 1 will change state. Whilst the same message is

being decoded the relay will not change state again. However, if another function-line (e.g. S1) is taken

high whilst S0 is still held high, it will cause a new transmission with new hop-code and new function

code (S0, S1). On reception of this message Relay 2 will change state but so will Relay 1, since the new

message contains S0 and S1, which toggles Relays 1 and 2 of the KDEC.

KDEC optimised for KFX2 (being a key-fob transmitter with up to 5 buttons) deals with this issue by not

responding to additional button-presses whilst one button is already pressed. However, this is at the

expense of removing transparency to the function-code being received. The user may require more than

one relay to be activated at once: in this case, KFX2 optimised mode should be used.