Final answer:
The 'Send' indicator light on a cable modem shows whether the modem has a good upstream connection. A solid 'Send' light indicates a successful upstream connection, while a blinking light means it is still trying to connect.
Step-by-step explanation:
When troubleshooting cable modem connectivity, it is important to understand the role of each indicator light on the device. A cable modem typically has several lights that indicate different operational statuses. The indicator light that shows whether the cable modem has a good upstream connection is the "Send" light. If this light is solid, it indicates that the modem has established a successful upstream connection with the Internet service provider's network. If it is blinking, the modem is still trying to establish a connection. The other lights such as 'Receive,' 'Online,' and 'Power' signify downstream connection, the modem's overall connectivity to the internet, and the power status, respectively.