SELECT DTMF Selective Calling Decoder / Loudspeaker User manual
Contents
1. Albrecht Kommunikationstechnik aus Norddeutschland SELECT DTMF Selective Calling Decoder Loudspeaker User manual General description and installation Select DTMF is a multi purpose extension speaker system for nearly any kind of 2 way radio with built in selective calling decoder for 4 digit DTMF codes The system works as a normal extension speaker suitable to 4 8 Ohms output 4 Watts with push buttons for manual on off auto switch on after correct code decoding and call LED The speaker can be connected to the radio receiver output by means of the speaker cable with 3 5 mm standard speaker plug The audio connection is earth free and can also be used in simple CB radios where the audio amplifier is also used as modulation amplifier Additionally the decoder unit requires 12 V DC connection Please use the same power supply as for the radio wherever possible The red wire must be connected to and the black wire to The unit has a short circuit and wrong polarity protection If the fuse should blow please replace only by the correct original fuse value never use more than 1 Amp fuse and never use any jumper across a fuse as a replacement The supply voltage is 10 16 Volts normal car battery range The DTMF system how it works On the rear side of Your speaker You will find a sticker with the factory pre installed individual calling numbers for example 1234 If properly installed the speaker will be of2. f initially You can switch the speaker on and off any time by pressing the appropriate push buttons Please set the volume to the desired value the decoder will need a certain minimum loudness value off course To reach highest sensitivity it is possible to leave the squelch open Press the off button The speaker will be muted and You are no more disturbed by any conversation or noise on the radio channel If a distant party wants to reach You he must use a DTMF keyboard microphone or simply a handy telephone dialer which has to be coupled acoustically to the microphone The correct number in our example 1234 must be pressed on the keyboard in sequence in the same way as known from the push button telephones In case of much interference on the radio channel it is desirable to press each digit of the code consequently about 1 1 second The maximum dialing pause between 2 digits should be less than 5 seconds If the correct code in the example 1 2 3 4 is detected by the decoder in Your speaker the speaker will automatically switch on and You can hear the conversation on the channel The CALL LED will be on and can remember that You have received a call You can answer Your call and after the conversation is finished press the off button to mute Your speaker again Also call LED will be off again Please do not forget to switch on Your speaker manually any time You want to start any transmission from Your side The DTMF select
3. ive call system uses the same standard tone dialing system which is used in most public and private telephone networks In this system any digit of a telephone number is represented by 2 simultaneously transmitted different tones The systems assures high sensitivity and accuracy and an optimum wrong code rejection when used in radio communication Changing the individual code The code printed on the rear side of the speaker is individually factory pre programmed Because 4 wire jumpers 1 wire for each digit are used for this hardware programming the individual code will never be lost even not during power supply failure or anything else The factory will use an individual code for each produced system out of more than 6000 possible decoder codes so there is a large security that nobody else in Your receiving range will use the same code However if You should wish a certain special code it is possible to modify the wiring accordingly Please note that all combinations of digits 1 9 are possible The digits 0 and cannot be used because of technical reasons Even codes like 1 1 1 1 or 9 9 9 9 are possible Modification of code programming should be doen only by qualified service personel because it requires knowledge in soldering on printed circuits boards Open the speaker and take out the decoder PC Board On the soldering side You will find 4 coloured wires which will connect the four positions M1 M2 M3 M4 with the app
4. ropriate soldering points for the digits 1 to 9 In our example 1 2 3 4 wire 1 first digit of the code M1 is connected to wire 2 second digit of the code M2 is connected to wire 3 third digit of the code M3 is connected to wire 4 fourth digit of the code M 4 is connected to If you desire the new code 5 6 7 8 then re solder as follows wire 1 first digit of the code M1 is connected to wire 2 second digit of the code M2 is connected to wire 3 third digit of the code M3 is connected to wire 4 fourth digit of the code M 4 is connected to
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