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Chapter 9, 264 Using the Analog Call Processing Subsystem
Using the CALL BIT Screen
System Operation When Data Spec Field Set to Bits
When the Data Spec field is set to Bits, the Test Set builds the signaling
messages using only the bit patterns set on the CALL BIT screen whenever a call
processing function is executed which uses any of the available messages. The
Test Set calculates the contents of the Parity field using the coding algorithms
specified in the industry standard for the selected system (that is, the system
specified in the System Type field on the CALL CONTROL screen).
By definition, the Test Set must meet the timing requirements of the industry
standard for the selected system. Therefore, depending upon the state of the Call
Processing Subsystem (i.e. Active, Register, Page, Access, or Connect) and the
frequency with which a particular call processing protocol uses a particular
message, it may not be possible to modify the contents of more than one field in a
message before it is sent to the mobile station.
For example: in the AMPS system, the system parameter overhead message must
be sent every 0.8 +/- 0.3 seconds on the forward control channel. Given this
timing requirement it is highly unlikely that, while in the active state, a user could
modify more than one field before the message was sent to the mobile station.
There is no functionality in the Test Set to allow an entire message to be modified
and then inserted into a messaging protocol at a specific location at a specific
time. This functionality requires a protocol analyzer.
When in the Bits mode the Test Set provides the messaging protocol for the user
(that is, for a desired call processing function the correct message(s) will be sent at
the correct time(s) according to the standard). It is the responsibility of the user to
generate the contents of all the messages which will be used in a particular call
processing function.
For example: if the Call Processing Subsystem was in the active state and the
operator wished to register the mobile station from the Bits mode, the user would
have to set the contents of all the messages used in the registration before
selecting the Register field to start the registration process.
NOTE:
No error checking is done on the bit patterns. The bit patterns are used but are not checked
against any industry standard. It is the responsibility of the user to ensure that the bit
patterns set in the CALL BIT screen are correct when the Data Spec field is set to Bits.
Unexpected operation of the mobile station can occur if the contents of the signaling
messages are incorrect.
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