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现有的长途电话线路多采用频分多路复用载波方式,这种方式中使用量最大的是通路变换装置。日本现有的通路变换装置是67年开始商用的VR—1型设备。最近几年CCITT提出了为改善国际通信网路链节的传输特性,有效地利用局内占地面积,以及经济的电源设备,因此希望采用小型化和低耗电的通路变换装置。 另一方面,作为通路滤波器,以混合集成电路为代表的元器件技术有了显著的进步。随着装配技术的提高,日本电气公司于75年10月研制了VR—2型新的通路变换装置。这种新装置的特点是: 1.电气特性 总的杂音,带外无用信号特性,群迟延失真等均满足CCITT的新建议,从而大大提高了设备的性能。 2.变换方式 VR—1型设备的通路滤波器采用LC滤波器,变换方式采用前群调制方式(3×4调制方式)。而VR—2型采用小型的、高性能的、便于大规模生产的有极性机械滤波器,其调制方式采用能充分发挥机械滤波器特性的预调制方式(1×12调制方式)。预调频率从稳定度好、基群滤波器易实现等考虑选128KHz。 3.采用架内分散安装方式 局内电缆的连接从VR—1型架上集中安装方式改为实际装配效率高、易于安装和维护的架内分散安装方式。这样不会因系统的增加,对架内布线、连接器、单元组件的要求过于复杂而增加初期投资。 4.高密度的装配 VR—2型设?
The existing long-distance telephone lines mostly adopt the frequency division multiplexing carrier way, and the most used way in this way is the path changing device. The existing path changer in Japan is a commercial VR-1 type device that started 67 years ago. In recent years, CCITT has proposed to improve the transmission characteristics of international communication network links, make effective use of the office space and economical power supply equipment, and therefore, it is desirable to adopt a compact and low-power path changing device. On the other hand, as the pass filter, hybrid ICs represented by the component technology has made significant progress. With the improvement of assembly technology, Nippon Electric Company in October 75 developed the VR-2 type of new channel change device. The new device is characterized by: 1. The electrical characteristics of the total noise, out of band signal characteristics, such as group delay distortion to meet the new CCITT recommendations, thus greatly improving the performance of the device. 2. Conversion method The channel filter of VR-1 equipment adopts LC filter, and the conversion method adopts front group modulation method (3 × 4 modulation method). The VR-2 uses a small, high-performance, large-scale production of a polar mechanical filter, the modulation used to take full advantage of mechanical filter pre-modulation (1 × 12 modulation). Pre-tune the frequency from the stability is good, the basic filter easy to implement considerations such as selection 128KHz. 3. The use of decentralized installation within the framework of the cable connection from the VR-1-type rack on the centralized installation to the actual assembly of high efficiency, easy installation and maintenance of the rack decentralized installation. This will not increase due to the system, the cabling, connectors, unit requirements are too complicated to increase initial investment. 4. High-density assembly VR-2 type set?