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美国CTS振荡器选型列表，美国CTS公司是一家超级专业化的元器件供应商，主要向广泛应用市场提供极其具有价值的产品线为主，经过长期的沉淀，如今的CTS已有极大的突破，尤其在制作高质量的OSC晶振产品更是将其的实力展示一览无遗，凭借着自身对于元器件行业的热爱，源源不断创造价值的同时，也行业开创大量创新型的产品，这是产品使得CTS公司的发展进行新的阶段，也使得其名气暴涨，也为其的发展打下极好的基础。

Clocks for North American synchronized networks are categorized into four basic “stratum” levels (i.e., stratum 1, 2, 3 and 4), where stratum 1 clocks are the most accurate and stratum 4 clocks are the least accurate. In addition to these four basic levels, there are two enhanced stratum classifications (i.e., stratum 3E and 4E), a level for Transit Node Clocks (TNCs) that falls between the stratum 2 and 3 levels, and another level for SONET Minimum Clocks (SMCs) that falls between the stratum 3 and 4 levels. All of these levels (which are described further below) have been standardized and their basic performance parameters are defined in ANSI T1.101. In general, the performance parameters for the various levels have been established to assure that synchronization can be transmitted through the network from the most accurate clocks, through intermediate clocks, to the least accurate clocks. 

北美同步网络的时钟被分类为四个基本的“阶层”级别（即。层1、2、3和4），其中层1时钟最准确，层4时钟最少精确的除了这四个基本层次之外，还有两个增强的地层分类（即3E和4E），位于层2和层3级别之间的传输节点时钟（跨国公司）的级别，以及另一个位于层3和4级别之间的SONET最小时钟（SMC）的级别。所有这些级别（将在下文中进一步描述）已经被标准化，并且它们的基本性能参数是定义见ANSI T1.101。一般来说，已经确定了各个级别的性能参数为了确保同步可以从最准确的时钟通过网络传输中间时钟到最不精确的时钟。
Stratum 2, 3E and 3 clocks form the major distributive part of service provider synchronization networks. These clocks are generally deployed in NEs (Network Elements) in pairs (i.e., as independent, redundant units, each of which consists of an oscillator and the functions for controlling that oscillator).

层2、3E和3时钟形成了服务提供商同步网络的主要分布部分。这些时钟通常成对地部署在网元（网元）中（即，作为独立的、冗余的每个单元由一个晶体振荡器和用于控制该振荡器的功能组成）。
In general, the stratum 3E level was defined to be compatible with previously existing stratum 3 clocks (i.e., it has the same pull-in/hold-in requirements as stratum 3). However, the stratum 3E requirements on filtering of wander and holdover are significantly tighter than those for stratum 3. GR-436-CORE recommends that stratum 3E clocks be the minimum clocks used for Building Integrated Timing Supply (BITS) applications. In addition, it is recommended that stratum 3E or higher quality clocks not be used in NEs other than a BITS (e.g., it is recommended that transport NEs use stratum 3 or lower quality clocks).

一般来说，层3E级别被定义为与先前存在的层3时钟兼容（即具有与地层3相同的拉入/保持要求）。然而，地层3E对过滤的要求漂移和滞留明显比地层3的那些更紧密。GR-436-CORE建议第3E层时钟是用于楼宇集成定时供应（BITS）应用的最小时钟。在里面此外，建议在BITS以外的网元中不要使用第3E层或更高质量的时钟或石英晶体振荡器（例如，建议传输网元使用第3层或更低质量的时钟）。
The accuracy of a clock is a measure of its ability to generate, in the absence of any reference, a frequency as close as possible to the nominal frequency. Frequency accuracy is expressed and defined quantitatively in terms of maximum fractional frequency offset, as discussed in Section 3.2. Table 4-1, 4-4, 4-7 lists the freerun accuracy values for the various clock stratum levels (Stratum 2, 3E, 3).

时钟的准确性是衡量其在没有任何参考的情况下产生频率的能力尽可能接近标称频率。频率精度在最大分数频率偏移项，如第3.2节所述。表4-1、4-4、4-7列出了各种时钟阶层级别（阶层2、3E、3）的自由运行精度值。
Free-run accuracy represents the maximum long-term (20 years) deviation limit from the nominal frequency with no outside frequency reference (Free Run Mode).

自由运行精度表示与标称频率的最大长期（20年）偏差限制没有外部频率参考（自由运行模式）。

Accuracy is used in this document to indicate the degree to which the frequency of a clock may deviate from its ideal or desired value. Accuracy is usually used to specify the frequency deviation of a clock in the free-run mode. (See Section 3.6 for a discussion of modes.) Accuracy is defined such that the magnitude of the fractional frequency offset of a clock does not exceed the specified number, where: fractional frequency offset = (f-fd)/fd f = actual frequency output of a clock fd = ideal or desired frequency.
本文件中使用精度来指示时钟频率可能偏离的程度其理想值或期望值。精度通常用于指定自由运行中时钟的频率偏差模式（有关模式的讨论，请参见第3.6节。）定义精度时时钟的分数频率偏移不超过指定的数字，其中：

分数频率偏移=（f-fd）/fd
f=时钟的实际频率输出
fd=理想或期望的频率。

Drift is a measure of how a clock’s frequency accuracy (or offset) changes with time. Drift is typically used (along with an initial holdover accuracy or offset limitation and possibly a temperature-related factor) to limit the frequency offset of a clock in the holdover mode.

漂移是衡量时钟频率精度（或偏移）如何随时间变化的指标。通常使用漂移（连同初始保持精度或偏移限制以及可能的温度相关因素）保持模式中时钟的频率偏移.