Operating instructions

OPERATING MANUAL 2945A
46882-311D 4-15
AF test mode
The AF TEST mode requires a signal source to apply to the circuit or equipment under test and a
measuring facility to analyse the resultant output signal.
The signal source is provided by the audio generators as for the Tx TEST mode and the AF
measuring circuits configured as for the Rx TEST mode. The RF generator and IF local oscillators
are disabled. The power metering and modulation metering functions are also disabled.
Systems mode
The systems mode of the Service Monitor allows the instrument to test communications equipment
which is designed for operation on dedicated systems such as cellular mobile radio telephone
systems and trunking radio telephone systems. Automatic testing is performed using various test
programs. These can be made to check all functions of the system, the signalling only or any
intermediate choice of functions, depending on the user’s requirements.
The data processing needed to carry out these tests is handled by a 68000 microprocessor and three
Digital Signal Processors (DSPs) on the cellular radio systems board B3/1.
The board has 1 M byte of EPROM which contains the cellular systems software and the built-in
test sequences.
The user defined sequences and user set-ups are held in 256 k byte of NOVRAM.
One of the DSPs generates the signals required to simulate the system signals, the other two handle
the signals received from the mobile.
A gate array is used for communication between the 68000 microprocessor and the DSPs.
Interfacing between the digital circuits on B3/1 and analogue circuits of the Service Monitor is
handled by a dual 18-bit digital to analogue converter for the Service Monitor to mobile signals
and by a 12-bit analogue to digital converter for signals from the mobile.