User Manual

Central Terminal Level Control Unit
Operators Manual
GSI 002
605-0000-428
Issue 1.2. Date 5/11/98
Page 3 of 14
3. Principles of Operation
The Level Control Unit periodically acquires a full low rate RF downlink /
uplink through RF cabling coupled into the CT transmit / receive antenna
ports. Knowledge of the path loss between the Level Control Unit and RF
antenna port allows the LCU to instruct the Shelf Controller to adjust RF
receive level as required.
The alpha-numeric display using menu driven selections with the keypad
provides:
• Input and read-back of set up information regarding RF component losses,
frequency, PN code.
• Output information on the Level Control Unit status and the status of each
RF channel.
To allow a specific RF channel to be quickly adjusted during commissioning
(or re-checked by a visiting maintenance engineer) a “continuous mode” of
operation (selected using the handheld terminal) enables downlink
transmission on the code specially allocated for gain adjustment purposes. The
Level Control Unit scans and acquires a CDMA link, status information such
as confirmation of control loop convergence is displayed. Once control loop
convergence has been confirmed the Shelf Controller mode is set to “Polled
Mode”by the operator for normal background control of the receiver gain of
each RF channel. Polled Mode settings of once per hour or once per day are
supported
Note 1: If the LCU is left in continuous mode for more than 1 Hour, the shelf
controller will disable the downlink to prevent the LCU using the radio
channel indefinitely.
Note 2: The transmission of the CDMA code signal for the link to the Level
Control Unit from each Modem shelf is supported using Modem number 16
which is also used to provide automatic Modem sparing. If the circumstances
exist that the spare modem is required to function in place of a faulty modem,
the automatic receiver gain control is suspended for that modem shelf until
Modem 16 becomes free again.