Bradley 233 - Afunctions

"Ext Trig" it depends on the frequency of the external signal applied to the input socket,
and on "Single Cycle" on the rate of pressing the Manual (Red) button).
The duty cycle of the rate signal is of interest because the output sections can be
driven directly by this rate signal by selecting "squarewave" at the output. On "Free
Run" the duty cycle is approximately 50%, i.e. a squarwave. On "Ext Trig" it is the
same as the external signal, if this is a pulse of fast rise time, but this will depend on
the setting of the "Level" control particularly if the edges are slow. Selecting negative
"Slope" converts the signal to its logical complement. On "Single Cycle" the signal is
a pulse of width equal to the time that the manual button is held in.
The pre-pulse and the A delay are both initiated by the positive edge of the rate signal.
2. B Section
On "Parallel Delay" the B delay is also initiated by the positive edge of the rate signal.
On "Serial Delay" the B delay starts at the end of the A width.
When "Gated By Width A" is selected, the B delay becomes an oscillator gated on
synchronously by the A width.
By pressing both the "Parallel Delay" and "Gated By Width A" buttons, control of the
"B" oscillator is released by the 'A' section thus allowing the 'B' oscillator to free
run.
3. Output Sections - See Fig. 7
The A and B widths drive the output sections via a logical OR function. When neither
is selected the rate signal drives the output (see 3.4.1). The "Comp" function, when
selected, inverts the signal before it reaches the output amplifier.
The output stage is a current source (high impedance) with a shunt 50fi resistance,
(which can be switched out with the cover removed, see 3.7.7). This type of output
can drive resistive and reactive loads of any magnitude without limiting. The output
impedance at the end of any length of 50i2 cable is therefore always 50J2 and resistive,
whatever the terminating impedance. This is because all reflections are absorbed at
the generator.
On "Sum" the two output current sources are switched into output 2, shunted by only
one 50fi resistor.
3.5 'A'FUNCTIONS
3. 5.1 Free Run
This function selects the internal oscillator, (whose rate is controlled-by the "PERIOD"
switch and vernier) as the main signal source for the instrument.
3. 5. 2 Square-wave
Select "Free Run", and "Square-wave" on the output in use. All delay and width controls
are then ineffective on that output. Nevertheless, at high frequencies it is advisable to set
them all to minimum, to prevent the chance of visible sub-harmonics on the output signal.