# External Tally Support Some sending might have knowledge of whether they are on output that might come from another non-NDI device. In effect, the sender side wants to indicate how it is known to be used and have that be reflected both to the local device but also down-stream in the "echoed tally messages". To achieve this there is a function on the sender side that updates the tally state. ``` bool NDIlib_send_set_tally( NDIlib_send_instance_t p_instance, const NDIlib_tally_t* p_tally ); ``` This function will "reference" count the local tally and the remote tally to give an indicator both on the local device and on the remote connections on the combined NDI and local tally values. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.ndi.video/all/developing-with-ndi/advanced-sdk/external-tally-support.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.