Bradley 233 - Bfunctions; Output Functions

are all out. The red button can then be used to gate the "PERIOD" oscillator, in a manner
similar to a morse buzzer.
3.5.13 Pre-pulse
The pre-pulse is useful for triggering oscilloscopes, circuits under test or other pulse
generators at "zero time" with respect to the delayed output pulse. It is a positive going
pulse of greater than 2V into an open circuit or IV into 5012. It is not necessary to terminate
the cable, provided that it has a characteristic impedance of 50S2. At low frequencies the
pulse width is about 250nsec so that it is easily visible on an oscilloscope, and has enough
energy to trigger medium speed devices. At higher frequencies the pulse width reduces to
lOnsec at 50MHZ.
3.6 'B'FUNCTIONS
3. 6.1 Parallel Delay
On parallel delay the A and B delays start simultaneously, on the trigger from the PERIOD,
input signal or from the action of the manual button. This allows one pulse to be delayed
"through" the other.
3.6.2 Serial Delay
In this mode the B delay is initiated by the trailing edge of the A width, allowing a pulse pair
to be moved as a group, using the A delay control.
3.6.3 Internal Burst
Selecting "Gated By Width A" converts the B delay circuit to an oscillator, synchronously
gated by the A width. Select only B width on the output unit. Keep the B width setting roughly
the same as the B period setting. Ensure that it is not dividing the frequency by being set too
wide. Set the A width to at least ten times the B period. Then make fine adjustments as
necessary.
3.6.4 Two Frequency Sources
Press "Parallel Delay" and "Gated By Width A" simultaneously so that they both remain in.
The B period oscillator will then free-run. There is a slight tendency for the oscillators to
phase lock to the same frequency or to a low order sub-harmonic, particularly at high fre
quencies, but for most purposes this effect will be negligible, and probably not noticeable.
3.7 OUTPUT FUNCTIONS
3.7.1 Signal Source Selection
The A and B buttons on each output section determine whether the output pulse is width A,
width B or both. When both A and B are selected on one output, there will be no increase in
amplitude where the pulses, overlap. The two pulses are combined by a logical OR function
before the output amplifier, whose two output level states are set by the offset and amplitude
controls.
A square wave will be obtained when both A and B buttons are out and "Free Run" is selected.
In the "Ext Gate" mode this will become an interrupted square wave - if an external input
signal is present and the level control is correctly set. On "Ext Trig" or "Single Cycle" the
output state will depend on the input state, or manual button position.