Carrier machine is a transmission device for multi-channel telephones, which applies the principle of frequency division multiplexing and can transmit multiple telephones on one or two pairs of lines. A carrier machine that uses open wire as the transmission medium. The transmission line is a copper wire with a diameter of 3mm. The multiplexing frequency of the open line carrier machine can reach 500 kHz and can transmit 40 calls. Open line carrier machines usually use a dual band two wire system. Symmetrical cable carrier machine is a carrier machine that uses symmetrical cables as the transmission medium. The cable is a high-frequency symmetrical cable with a wire diameter of 0.9~1.2 mm. The symmetrical cable carrier machine is superior to the open line carrier machine in terms of communication capacity, anti-interference, and confidentiality. Most cable carrier machines adopt a single band four wire system. A coaxial cable carrier machine that uses coaxial cables as the transmission medium. The small coaxial cable used in railway communication has a coaxial tube size of 1.2/4.4, which means the diameter of the inner conductor is 1.2mm, the inner diameter of the outer conductor is 4.4 mm, and the physical impedance is 75 Ω. It is generally used starting from 60 kHz. The small coaxial cable carrier communication adopts a single band four wire system. There are 300 and 960 small coaxial cable carriers used in railway communication, with amplification distances of 8 km and 4 km, respectively
Function of testing report:
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1. Telephone communication and confirmation of requirements
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1. The testing industry is fully covered, meeting different testing needs
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