Recycling by product massive number of types of plastic, they each carry a resin identification code, and must be sorted before they can be recycled. This can be costly; while metals can be sorted using electromagnets, no such 'easy sorting' capability exists for plastics. In addition to this, while labels do not need to be removed from bottles for recycling, lids are often made from a different kind of non-recyclable plastic. To help in identifying the materials in various plastic items, resin identification code numbers 1-6 have been assigned to six common kinds of recyclable plastic resins, with the number 7 indicating any
Automatic Transmitter Identification System (marine) to a value of 121. While DSC transmissions take place exclusively on Channel 70, the ATIS digital signal is transmitted on the same VHF channel as the voice transmission: it lasts for 285 milliseconds after the PTT button has been released, using frequency modulation frequency-shift keying (FSK) between the frequencies of 1,300 Hz and 2,100 Hz at 1,200 baud. The core part of the message is transmitted using 10-bit codes; each code being formed of a 7-bit symbol followed by a 3-bit count of the number of zeros in that symbol. Automatic Transmitter Identification System (marine) The Automatic Transmitter Identification