首先，JRC JCY-1900的设计依据是“IEC 61996-1-2013”和“MSC+333(90)”这两个规范文件，我们打开IEC 61996-1-2013文件在文件的16页4.4.4 Recording integrity（记录完整性）：中提到以下内容：
4.4.4 Recording integrity
(See 6.1.10)
(MSC.333(90)/5.3.3) The recording method shall be such that each item of the recorded data is checked for integrity, i.e. it is identical to the data being received, and an alert according to
IMO A.1021(26) given if a non-correctable error is detected.
The VDR shall automatically continuously monitor the following:
>power supply;
>record function;
> microphone functionality.
Malfunction of any of the above shall generate a caution (see 3.1.4). The caution shall remainuntil the equipment is serviceable. It shall also indicate its caution status by means of contacts of a relay (or equivalent) which is held energized in the no-alert condition.
The VDR shall also continuously monitor the period of data stored on each element of the final
recording medium. If the period of any of the elements falls below the minimum compliantperiod defined in 4.5.4 a caution shall be generated and remain while the condition is true.
文中例举的三种内容有如有问题会产一个“caution”警告，它caution在内容在3.1.4中有说明，引用如下：
caution
lowest priority of an alert. A condition which does not warrant an alarm or warning condition,
but still requires attention and out of the ordinary consideration of the situation or of given information
文中并没有要求有一个声音的报警，但要给出对应的信息。比caution还要高还有两个级别，分别是alarm(最高)和waming(次高)。
如船上的BNWAS报警，这内容应划入“record function”只是众多记录信息的一种，这信号的丢失只会引起一个“caution”，所以只有提示是正常的。
其次，我们看了一JRC的INSTRUCTION MANUAL安装手册，对应的版本号是CODE No.7ZPNA4384B FEB. 2017 Edition 3，手册的第27页也有厂家的解释，摘录如下：
4.3.1 The outline of alerts
The alert has two types: WARNING alert and CAUTION alert. The WARNING alert has higher
priority than the CAUTION alert. If the WARNING alert occurs, the alert sound sounds. Approving
the WARNING alert or solving the WARNING alert, the alert sound goes out.
JRC 的JCY-1900也是按以上规范进行设计的，只有报警级别是WARNING才有声音提示，如果是CATION也是只有信息提示没有报警声音。再从手册的95页到100页有更加详细的报警类型，从表中可以发现，如果是一般传感器信号丢失对应的报警类型就是CATION，所以BNWAS信息只有信息不会有声音提示。
新规范的目的使VDR真正作为一个记录工具而不是一个综合的报警系统，不需要产生过多的报警声音以免引起驾驶员的频繁复位，从而使驾驶员更专注于航行，提高航行安全。
