Tone Mode
General
In Tone mode the generator output is stepped through a user-defined list of up to 16 frequencies
under the control of a signal applied to the TRIG IN socket. A true level at TRIG IN will output the
tone; a false level will stop the tone and switch the generator to the next frequency on the list
ready for the next true level. A logic high level will be true if the
slope
is set to
positive
on
the
TRIGGER INPUT SETUP
screen and a logic low level will be true if
slope
is set to
negative
.
All standard and arbitrary waveforms can be used in Tone mode with the exception of pulse,
pulse-train and sequence. During Tone all waveforms are generated in DDS mode for fast phase-
continuous switching between frequencies. For DDS operation all waveforms must be 4096
points in length; this is the natural length for standard waveforms but all arbitrary waveforms are
expanded or condensed in software to 4096 points when the Tone list is built. This does not affect
the original data.
Because DDS mode is used the frequency range for all waveforms is 1mHz to 10MHz in Tone
mode, including triangle, ramp and squarewave which have different limits in continuous
operation.
The minimum time per step is 20ms (tone time plus off time); the minimum tone time is 2ms and
the minimum off time is 2ms.
Tone Setup
Press the
tone setup…
soft-key on the
MODE
screen, called by pressing the MODE key, to get
the
TONE SETUP
screen:
TONE SETUP: done
◊
◊
2·000000 kHz #2
♦
3·000000 kHz del
◊
◊
end of list #4
Each frequency in the list can be changed by pressing the soft-key and entering the new value
from the keyboard. The selected frequency can be deleted from the list by pressing the
del
(delete) soft-key. Additional frequencies can be added to the end of the list by selecting
end of
list
with the appropriate soft-key and entering the new frequency from the keyboard.
The whole list can be scrolled back and forward through the display using the rotary control.
When the list is complete, press the
done
softkey to return to the main
MODE
screen from which
Tone mode can be turned on and off.
Connections for DTMF Testing. Sync Out and Trig In
The main use of Tone mode is DTMF (Dual Tone Multiple Frequency) testing in which 2 (or more)
generators are set up with equal length lists of different frequencies and are triggered from a
common signal. The outputs are summed together by connecting the output of one generator to
the VCA/SUM IN of the other. DTMF testing generally uses sinewaves in the frequency range
600Hz to 1·6kHz.
The frequency lists are set up with one of each frequency pair in the corresponding position in the
frequency list, see Tone Setup above. The lists must have the same number of frequencies. Tone
mode is turned on by pressing the
tone
soft-key on the
MODE
screen, called by pressing the
MODE key. When Tone is first turned on, and at any other time
tone
is pressed, the generators
are set to the first frequency in the list (with the tone off) ready for the first trigger signal; pressing
the
tone
soft-keys on both generators is the way to re-synchronise the frequency lists should
they have got out of step for any reason.
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