Siemens SINUMERIK 840D sl Commissioning Manual page 890

Appendix
A.1 Abbreviations
TCU Thin Client Unit
TFTP Trivial File Transfer Protocol: Very simple data transmission protocol
UDP User Datagram Protocol: NTP is mostly processed via UDP.
USB Universal Serial Bus
UPS Uninterruptible power supply
UTC Universal Time, Coordinated: Coordinated Universal Time (previously: Greenwich Mean Time)
VNC Virtual Network Computing
94
Commissioning Manual, 03/2013, 6FC5397-1DP40-3BA1
NCU operating system (IM7)