| The universal Demag DRC-MP radio control |
Frequency hopping
For transmission of the radio signals between transmitters and receivers the so-called 433 MHz ISM band (ISM Band = Industrial Medical and Science Band) is used. Within the ISM band, 30 frequencies are alternately used in a pre-defined sequence (frequency-hopping). A random generator defines the sequence of the frequencies when radio transmission is started. Multiple transmission of the information is used in order to increase transmission reliability. Owing to this principle in conjunction with frequency-hopping, a high resistance against interference is achieved.
Frequency hopping is used for the first time for Demag DRC radio control systems, types D1-FH and D2. For type D1, the frequency of the radio signal is not changed during a transmission cycle. Frequency-hopping transmission features the major advantage that special information contents are transmitted on several physical channels. Thanks to this redundant radio transmission ¹, an extremely high resistance of radio transmission against other transmitters or electromagnetic interferences is achieved.
¹ Special information contents are transmitted on up to 5 different frequencies. Communication would only be interrupted, if (theoretically) all frequencies used are occupied by other radio systems or are malfunctioning.
