电码化技术的发展经历了固定切换电码化、脉动切换电码化、叠加移频电码化、预叠加移频电码化、车站接发车进路电码化、闭环电码化六种类型。
1
电码化就是通过轨道电路的转发或叠加机车信号信息技术的总称[1]。站内电码化预发码技术主要应用于铁路站内，它能保证站内正线电码化轨道电路连续不断地向机车车载设备发送所需的电码化信息，是行车指挥系统的基础设备之一。
1.1
我国铁路信号电码化技术源自于前苏联。二十世纪五十年代初，开始实施“50Hz交流计数电码化”计数，二十世纪七十年代初开始实施“移频电码化”技术，二十世纪八十年代开始实施“25Hz交流计数电码化”技术[2]。
摘要
本设计主要根据ZPW-2000A闭00A闭环电码化设计（下行），对电码化闭环检查的必要性、关键技术、电路原理和主要设计原则等方面进行了阐述。
G站ZPW-2000A闭环电码化设计（下行）包括说明书和图纸两部分。图纸部分包括12张：G站车站信号平面布置图、G站下行正向接车进路电码化电路图、G站下行正向发车进路电码化电路图、G站下行正线IG电码化电路图、G站侧线股道(3G、5G、7G)电码化电路图、G站闭环电码化N+1冗余发送电路图、G站闭环电码化机柜设备布置图、G站下行正线接车电码化检测电路图、G站下行正线发车电码化检测电路图和股道电码化检测电路图。说明书部分对每张图纸进行了详细的说明，平面布置图介绍了信号机，载频配置和补偿电容；正向接发车电码化和股道电码化介绍了与之有关的继电器电路以及它们的工作原理；机柜布置图则介绍了移频柜、检测柜和综合柜；N+1冗余介绍了载频切换和发码通道。
G station ZPW-2000A closed-loop code is designed to meet the“code for design of railway signal (TB 10007-2006)”requirement.
KeyWords:ZPW-2000A,Closed-loop code,Coding detection,N+1 redundancy
Two parts of the drawings and specifications areincluded in the G station ZPW-2000A closed-loop code design. Drawing part includesa total of 12: G station signal layout plan; G station downstream forward pick-up approach coding diagram; G station downstream forward departure approach coding diagram; G station downstream positive line IG coding diagram; G station side track (3G, 5G, 7G) coding diagram; G station closed-loop coding N+1 redundancy send diagram; G station closed-loop coding cabinet equipment layout; G station downstream positive line pick-up coding detector diagram; G station downstream positive line departure coding detector diagram and shares road code of detection circuit diagram. The description part has carried on the detailed instructions to each drawing. The signal, carrier frequency configuration and compensation are described in signal layout plan. Relating to the relay circuit and their working principle are introduced in downstream forward pick-up approach coding and departure approach coding diagram. Cabinet equipment layout introduced frequency shift cabinet, detection cabinet and comprehensive cabinet. Carrier frequency switching and hair code channel are introduced in N+1 redundancy.
G站ZPW-2000A闭环电码化设计满足《铁路信号设计规范(TB 10007-2006)》的要求。
关键词：ZPW-2000A；闭环电码化；电码化检测；N+1冗余
Abstract
The design completed the G station ZPW-2000A closed-loop code design (downstream) mainly based on the principle of ZPW-2000A closed-loop coding technology and the design of engineering graphics specifications, terms of the necessity of closed-loop checking code, key technology, circuit principle and main design principles are described.