transverse conversion loss  TCL 横向变换损耗
transverse conversion transfer loss  TCTL 横变换转移损耗
TCL (Transverse Conversion Loss) – DSX CableAnalyzer TCL is one of two balance measurements found in ANSI/TIA-568-C.2, ANSI/TIA-1005 and ISO/IEC 11801:2010. The other is ELTCTL.

The measurement is made by injecting a differential mode signal (DM) into a twisted pair, then measuring the common mode signal (CM) returned on that same twisted pair. The smaller the CM signal returned, the better the TCL measurement (balance).
 
翻译：测量是通过向双绞线注入差模信号（DM），然后测量同一对双绞线返回的共模信号（CM）。CM信号返回的越少，TCL参数就会越好，越平衡。

If it looks similar to a Return Loss measurement, you're right. Except a Return Loss measurement is made by injecting a DM signal into the pair and measuring the DM signal returned. Here we are measuring the CM signal returned which is TCL.

翻译：如果你觉得它像是回波损耗的测试，那你就说对了。回波损耗测试是通过向双绞线注入DM（差模信号）然后测试返回的DM信号，然而TCL是测试CM信号。

Field test requirements for ANSI/TIA-568-C.2 are deferred to ANSI/TIA-1152. At this time, TCL is not a field test requirement because until the DSX CableAnalyzer came along, no field test equipment vendor could perform a TCL field test. It is anticipated that other test equipment vendors will eventually offer TCL field measurements too. Field testers are normally capable of DM measurements only – the DSX CableAnalyzer is capable of both DM and CM measurements, hence its ability to measure TCL and ELTCTL.

翻译：对于ANSI/TIA-568-C.2现场测试要求直到ANSI/TIA-1152标准。在那个时候，TCL并不是一个现场测试的要求，因为没有现场测试设备供应商可以执行TCL现场测试，直到DSX-5000电缆认证分析仪的诞生。预计其他品牌测试设备厂家最终也将提供TCL现场测量。现场测试人员通常仅能DM测量 – 对DSX-5000电缆认证分析仪能够既DM和CM的测量，因此其有测量TCL与ELTCTL的能力。

If you wish to add TCL and ELTCTL to your standard Category 5e, 6, 6A or Class D, E or EA test, select your test limit under the folder in DSX called Balance Measurements and look for your test limit with a suffix of (+TCL):

翻译：如果需要对于Cat5e，Cat6，Cat 6A测试TCL和ELTCTL参数，你只需要再DSX-5000 的文件夹下面找到+TCL的后缀就可以了。

This will add ≈ 6.6 seconds to your AUTOTEST time.
TCL测试将增加6.6秒测试时间。
The suffix of (+TCL) indicates a standard ANSI/TIA or ISO/IEC test with the addition of TCL and ELTCTLmeasurements. ANSI/TIA-568-C.2 and ISO/IEC 11801:2010 only provide test limits for Channel measurements at this time. If you select a Perm. Link test limit, the TCL and ELTCTL measurements will be performed, but there will be no PASS/FAIL criteria applied. You will also see the Industrial Ethernet standards TIA 1005 with the different E1, E2 and E3 environmental TCL and ELTCTL limits.

翻译：有（+TCL）后缀的预示着ANSI/TIA或者ISO/IEC测试有这个规格。 目前ANSI/TIA-568-C.2 and ISO/IEC 11801:2010 仅仅提供信道测试的极限值，如果选择永久链路测试，TCL和ELTCTL也会被执行，但是不会有通过/失败的标准。同样你也会看到工业以太网标准TIA 1005 ，E1,E2,E3的标准的限制。
 
In the example below from a DSX-5000 CableAnalyzer, a Category 6A Channel was tested. With a margin of 5.4 dB (6 dB is a factor of 2), you can feel confident that this link will perform well, even in a noisy environment.
翻译：从下面DSX-5000的例子中可以看到，Cat 6A通道测试有5.4db的余量，你就不用担心了，因为这条链路表现非常好。即使在有噪音的环境下。