The Link Electronics LEI-592M IP Caption Processor - Master is used for serial communication between an SD / HD closed caption encoder and the source of the serial data via the internet. Equipped with an audio transreceiver for signal transmission, it eliminates the need for phone lines as well as an internet-capable encoder.
The system connects the master at the encoder location and input data at the serial port or audio jack is output through the serial port or audio jack of the slave, respectively.
With selectable baud rates of 1200, 2400, and 9600 and a selectable serial / USB port, the master unit supports 8-N-1 or 7-O-1 type of serial data. Data is transmitted through UDP (User Datagram Protocol), a simple message-based protocol that eliminates the need for a dedicated end-to-end connection. A serial tunnel is used to transmit aerial and audio data that can be encrypted and password protected via the web browser. Without including the latency of the internet, the audio latency is less than 0.2 seconds.
The address of the master unit is permanently stored in the flash memory of the slave unit to allow secondary units to connect to any primary unit. In case of an internet connection break, the unit configurations will be automatically reset and the connection will be established. The master unit is connected to a gateway router with port forwarding enabled; in the absence of a static IP for the router, a dynamic DNS service setup is needed.
When the processor is powered, the audio LED turns green to indicate a good connection between the master and slave, while it turns amber to indicate audio detection with a low volume.
Green and amber lights in the data LED indicate sent and received serial data, respectively. In addition to input volume controls, the master has a standard 3.5mm mono headphone jack.