transmission code

例句：

1. 1. The transmission code is a secret that only the sender and receiver know.
   传输代码是一个只有发送者和接收者知道的秘密。
2. 2.The transmission code was used to encrypt the message.
   传输代码被用来加密消息。
3. 3. The transmission code was changed to prevent interception.
   为了阻止截取，传输代码被更改了。