User's Manual Part 2

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Operation of the Manpack in Frequency Hopping Mode
To operate in frequency hopping mode one of the of ESU (Encryption
Synchronisation Units) supplied with the frequency hopping option must be plugged
into the ESU socket on the top of the 2090 manpack adaptor. The ESU acquires
satellite timing information so must be in view of the sky i.e. cannot be operated
inside buildings. To help with this an optional ESU extender cable is available (P/N
2090-01-09) to enable the ESU to be positioned outside if operating within a
building.
To operate the manpack in frequency hopping mode refer to the Section
“Frequency hopping” in this manual.