Timestamp endpoint
Summary
    | Data Type | stream | 
    | Data Flow | send-only | 
    | Class |  TickEndpoint | 
    | Built in | YES | 
    | Purpose | timestamp service | 
    | supported labels | tick | 
Data Structures
None.
Sent
none.
Responses
Local device timestamp sent every second whilst stream is open.
Timestamp is integer milliseconds since 1970 .
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