UHF Radio Command / Radio Alarm System
(Type 458-RC)

General

For the export market, a similar system operating in the 434MHz band will be available to special order.

Both the transmitter and receiver are housed in a robust plastic case (98mm x 61mm x 32mm) and powered by an internal PP3 (MN1604) Alkaline battery or an external DC supply.

The 10 milliwatt transmitter will provide a communications range of 300 - 1000 metres, depending on the type(s) of antennas used and the local conditions.

A higher power (500 milliwatt) command transmitter is presently under development for users who require even greater operating range.

Configurations available
At present, the 458-RC system is manufactured in two standard versions: a Radio Command system for remotely switching other electronic devices on or off, and a Radio Alarm system which is similar to the MINDA but capable of signalling over much greater distances.

Radio Command System

K-Tech will be happy to consider meeting special customer needs by building the transmitter and/or the receiver into larger cases capable of accommodating these (and other) extra components. Such a fully-featured command system could, for instance, enable the full remote control of a CCTV camera with On/Off, Pan left/right, Zoom in/out, Tilt up/down or similar to be achieved.

Command Receiver - RX 458RC
This can be used either with the short wire antenna supplied or, if greater range is required, with a more efficient external antenna connected by coaxial cable terminated in a suitable SMB plug.

The three-way screw terminal block on the receiver panel enables the fully isolated single-pole changeover contacts of a built-in latching relay to be used for directly switching an external load of up to 1A at 30V D.C. or 0.3A at 125V A.C.

For simplicity of operation, the receiver is not normally fitted with an On/Off switch.

When deployed, and using the battery economiser mode, its average current drain is only 2.5mA (the receiver is switched on for only 200 milliseconds every 2 seconds and only 'locks-on' if a valid code is received). This means that any transmission from a command transmitter has to last for at least 2 seconds to ensure that it will be 'captured' and decoded by the receiver.

Once a valid transmission has been recognised by the receiver it then 'stays awake' for a further period of time (set at 10 seconds but re-programmable if required) in case additional commands are to be sent. Any transmissions made during this period can be of quite short duration since the receiver is already 'awake'. Ten seconds after receiving the last valid transmission, the receiver then reverts again to battery economiser mode.

If receiver battery power economy is not an important consideration, the economiser can be disabled (receiver operates continuously drawing around 25mA) by adding a small internal shorting-link. This gives near-instantaneous switching on receipt of valid command signals.

Command Transmitter - TX 458RC
When the transmitter is used with the short rod antenna supplied, greatest operating range will be obtained when the unit is held so that the antenna is vertical and clear of local obstructions. If greater range is required, a more efficient external antenna can be connected to the transmitter by means of a coaxial cable terminated in a suitable SMB plug.

The standard transmitter case, because of its size, can only accommodate two push-button switches on its front-panel and, like the receiver, is not normally fitted with an On/Off switch. It does consume a very small amount of power all the while a battery is connected, but since this quiescent current drain is less than 50 microamps the battery life will not be seriously degraded in normal operation.

When operating the transmitter, it is important to remember that the receiver only 'wakes up' every two seconds to look for a signal so an initial command should be transmitted for at least two to three seconds to be sure of catching it when it is awake and listening.

When the transmitter battery voltage falls close to the point where its operation could be unreliable, the small red LED will only light dimly when a button is pressed, indicating that it needs to be replaced.

Internal/External battery power
All internal batteries that are fitted must be 9 volt Manganese Alkaline, type MN1604 (PP3).

If a 1.3mm barrel plug is inserted into the external power connector of a unit then its internal 9 volt battery will be automatically disconnected and the unit can then be powered from an external 6 - 12 volts DC supply (at 100mA maximum current).

NOTE: If it is necessary to switch off a unit completely when not in use, (rather than by removing the battery) a spare barrel plug can be left 'parked' in the power connector socket.

Radio Alarm System

The transmitter can also be provided (as an additional option) with a built-in 'Man Down' facility using a movement sensor which will activate the alarm if the person carrying the transmitter does not move at all during a pre-determined period.

A larger receiver designed for desktop or mobile use (identical in appearance to the MAXI-MINDA receiver) will shortly be available, having a number of additional facilities. Either receiver will be able to indicate the status of up to four suitably coded transmitters, and can, if desired, emit an audible bleep when a signal is received.

Alarm Receiver - RX 458RC
Each alarm receiver can display two status indications from up to four different alarm transmitters, coded 1, 2, 3 or 4.

The receiver can be operated either with the short wire antenna supplied or, if greater range is required, with a more efficient external antenna connected by coaxial cable and a suitable BNC to SMB converter lead (both obtainable from K-Tech as accessories).

Whenever the receiver is switched on, all of the eight large alarm status LED's will be briefly illuminated, in pairs, to provide a 'lamp-test' and give visual confirmation that the micro-processor is operating correctly. The small green 'Power' LED adjacent to the Reset push-button will remain lit to show that the receiver is being powered.

Briefly pressing the 'Reset' button will cancel any audible alert, initiate a 'lamp-test' and extinguish any alarm status LED's that may have been illuminated prior to resetting.

Confidence transmissions
A receiver can be programmed to expect regular 'confidence' transmissions from one or more of its associated alarm transmitters. If a transmission is not received from any unit within the pre-programmed time period set then the appropriate LED will begin to flash and an audible alarm will sound to alert the operator. To cancel this 'lost signal' alert the operator must press the 'Reset' button on the receiver. If this has not been done within a second pre-programmable period of time the receiver repeats the 'lost signal' alert and continues to do so at intervals until the operator does acknowledge the alarm by resetting the receiver.

Each of the four unit identities supported by a receiver can be independently programmed for the above option, or not, as required, and the 'lost signal' time period, and 'alert repeat' time period can be independently adjusted for each unit identity.

Transmitter low-battery alert
A valid transmission received from an alarm transmitter with a weak, but not completely flat, battery will cause the appropriate alarm-status LED indicator on the receiver to 'blink' out briefly about once per second. This will indicate to the operator that that particular transmitter should have its battery replaced at the earliest opportunity.

Channel-in-use indicator
The small red 'Signal' LED adjacent to the antenna connector will illuminate whenever a strong signal is received on the frequency to which the receiver is switched. This can be a useful indication to the user that local co-channel interference is present and that a change of operating frequency (of transmitter and receiver) may be advisable.

Battery
The alarm receiver operates from an internal 9 volt Alkaline battery (Duracell MN1604 or equivalent) which is capable of powering it for 18 to 20 hours of continuous use. To replace the battery, slide open the battery-box cover, lift out the battery and carefully remove the connector. Inspect the connector and, if necessary, adjust the position of the spring-leaves to ensure good contact, and snap it on to the new battery. Dress the leads to one side of the new battery and slide the battery-box cover on until it clicks into place.

Alarm Transmitter - TX 458RC
When the transmitter is used with the short rod antenna supplied, greatest operating range will be obtained when the unit is held so that the antenna is vertical and clear of local obstructions. If greater range is required, a more efficient external antenna can be connected to the transmitter by means of a coaxial cable terminated in a suitable SMB plug.

The standard transmitter case, because of its size, can only accommodate two push-button switches on its front-panel and, like the receiver, is not normally fitted with an On/Off switch. It does consume a very small amount of power all the while a battery is connected, but since this quiescent current drain is less than 50 microamps the battery life will not be seriously degraded in normal operation.

When operating the transmitter, if the small red LED fails to light, or is lit dimly when a button is pressed, the battery probably needs to be replaced.

Confidence transmissions / Alarm repeats
The Alarm Transmitter can be programmed so that for any or all of the four identities it can send a regular confidence (Green) transmission as an 'I'm here and OK' signal. If the companion Alarm receiver has been programmed (1) to remain silent whenever a valid 'Green' transmission is received, and (2) to signal an alarm if nothing is heard from one or more of its associated transmitters within a pre-designated period of time, then the following scenario becomes possible:-

* When an initial 'Green' transmission is received from any of its associated transmitters the receiver will remain silent and one of four pre-programmed internal time-clocks within it will start counting. Each subsequent 'Green' transmission from that same transmitter unit will again be received silently and reset the time-clock to zero. If, however, the pre-set time period elapses before another 'Green' signal has been received then the appropriate LED on the receiver will begin to flash and a 'Lost Signal' audible alarm will be signalled.

* Until the person using the receiver pushes the 'RESET' button to clear the audible and visual alarms, a warning alert tone will continue to be emitted at the pre-programmed interval(s).

* If a different transmitter unit (but of the same family) is then received, another time-clock commences operation independently in the same way as described above.

* If a valid 'Red' alarm signal is received from any of its associated transmitters the receiver will, of course, generate all of the normal audible and switching alarms.

* In a situation where the system is being used to protect a person close-by but out of sight, the regular confidence transmission will keep the receiver silenced all the while it is present. If the transmitter moves out of radio range, its battery fails, or it is otherwise disabled the receiver will emit an alarm signal as soon as the confidence signal has been missing for the pre-programmed period of time.

This enables, for example, a VIP to be protected at night by a bodyguard in an adjoining room or a person going into a potentially hazardous situation by a 'back-up' team in a vehicle close-by. The transmitter will send the confidence signals entirely automatically without disturbing the user unless he, or she, wishes to send a 'Red' alarm signal in the usual way.

Data coding
The 458-RC system uses a data coding format which is very similar to that used by MINDA and it can be programmed using the same interface kit.

For a system to operate correctly, both transmitter and receiver must:-

• have been programmed with the same Family ID code (see below).
• have the same frequency selected on their internal 4-way DIL switches.
• have the same Unit ID selected on the internal 2-way DIL switch.

IMPORTANT NOTE
All Transmitters and Receivers are usually programmed with the SAME Family ID Code so that they can, when required, work together. The Family ID code can only be changed by re-programming the appropriate units. If this should become necessary, they should be returned to K-Tech with details of the changes required.