DSR—User-Defined Keys (VT Level 4 Only)
The host asks if the user-defined keys (UDKs) are locked or unlocked.
(Host to terminal)
|CSI ? 25 n||The host asks if UDKs are locked or unlocked.|
(Terminal to host)
|CSI ? 20 n||UDKs are unlocked.|
|CSI ? 21 n||UDKs are locked.|