MITSUBISHI ELECTRONICS AMERICA, INC.
ST200 Series Technical Support Manual
22
January 2000
A 4-digit security code allows users to set call restrictions, change the 3-digit handset lock code,
reset an accumulated talk timer, and change the status monitor. Users can input their 4-digit
security code into the MT during NAM programming. Call restriction levels include: no
restriction, recall memory locations 1-99 only, and receive only.
The MT saves both the handset lock and the call restriction mode settings while off. For
maximum security, users should electronically lock the handset or select
receive only
call
restriction.
5.5.2 Authentication
Every MT authenticates its identity upon call setup and during commissioning and performance
verification tests. The authentication process encrypts a random variable and an Access Security
Key (ASK) to form an authentication code. The MT and CGS independently generate the
authentication code, with the MT sending its version of the code to the CGS at the beginning of
each call event. The CGS in turn verifies that the MT can continue call setup, commissioning, or
performance verification tests. The authentication code is both random and encrypted for each
event, with only the specific MT and CGS having all information required to produce the code.
5.5.3 Scrambling
All communications between a specific MT and the CGS are scrambled before transmission.
Because the scrambling function derives from a random number that each MT selects, only that
specific MT and the CGS can de-scramble intelligible communications.
5.6 Network Data Distribution & Storage
During initialization, and each time the MT is powered on, the CGS transmits network data to
that MT. This data includes network status, channel parameters, and signaling channel
assignments. The MT stores some of this data in Non-Volatile Random Access Memory
(NVRAM), retaining the information when powered down. For example, an MT saves the
system table
in NVRAM, defining the last beam and signaling channel used. The system table
helps the MT in the network acquisition process. The CGS continuously transmits detailed
system status and assignment information to operating MTs through the GC-S channel (idle MT)
or FES-C in-band signaling (active MT).
5.7 Shutdown Conditions
There are four conditions that may cause a MT to cease transmission or automatically shut down.
All dealers should be aware of and understand these conditions for trouble resolution and user
training.
