to TOTAL, distortion is measured on all transitions within the character, both M/S and S/M. When the switch is
set to EARLY or LATE, distortion is measured on all transitions (M/S or S/M) occurring early or late
respectively. Total, early, or late peak measurements will be retained on the front panel nixie display until
higher distortion is measured or until the display is reset, either automatically or manually. The TRANSITION
switch can be used to select any particular transition interval within the start-stop character for measurement.
e. Code Levels. The analyzer is designed to analyze all start-stop signals with code levels from 5 to 8.
The most common code is the 5 level Baudot code used in telegraph communications. A teletypesetter 6 level
code is also in general use. Start-Stop data transmission signals generally employ an 8 level code. It is
important to know the type of signal and the code level of the signal when operating the analyzer. Erratic
operation of the analyzer may result from improper setting of the CODE LEVEL switch.
f. Synchronous Operation. The analyzer has a built-in digital synchronizer designed to make its timing
circuits synchronize and follow the timing of an incoming signal. For proper functioning of the synchronizer, the
timing of the input signal must be within 0.1% of the analyzer timing. Only bias distortion measurements are
possible since there is no end distortion in a synchronous signal. To make the measurement, set the CODE
LEVEL switch on the analyzer to SYNC; the TRANSITION SELECT switch should be in the ALL position. The
reading on the nixie display will indicate the bias distortion contained in the synchronous signal. Peak distortion
measurements cannot be made until the analyzer has synchronized with the incoming signal. Synchronization
can be checked by measuring any cumulative bias distortion as indicated in g below. Synchronous signals may
also be analyzed on a start-stop basis using any of the positions of the CODE LEVEL switch. In this method,
the analyzer will select a M/S transition as a reference and measure the remaining transition times relative to it
for an equivalent character time as determined by the setting of the CODE LEVELS switch. It will then stop
and wait for the next M/S transition before starting another measuring cycle. This method will produce
satisfactory results except when there is a significant amount of fortuitous distortion in the signal.
g. Speed Error Measurement. Differences between the operating speed of the analyzer as selected by the
BAUD RATE switch and the incoming signal will introduce bias or end distortion. A faster incoming signal
introduces marking bias or spacing end distortion while a slower incoming signal introduces spacing bias or
marking end distortion. On a random signal pattern, the distortion measurement on each successive transition
within a character will increase when there is a difference in speeds. By using the TRANSITION switch, a
measurement can be made on each transition of the incoming signal to determine the distortion increase from
the first transition to the last. The amount of speed error in percent is one-fifth of the increase in distortion
reading from transition one to transition six. For example, a five-percent increase in marking bias distortion
from the first to the sixth transition would indicate the incoming signal is one percent faster than the operating
speed of the analyzer.
h. Analyzer Strapping Options. The analyzer is provided with a strapping option for the selection of a
spare operating speed. When the spare speed option is exercised the spare oscillator on assembly 2A2A7
produces an output at the crystal frequency (2A2A7Y3). This output is applied to the time base circuits, which
are also located on this assembly. Outputs from the time base circuits are available at 9 different frequencies.
Any one of these 9 frequencies may be selected by the spare speed strap to produce an output at 200 times the
desired baud rate.
3-9. Oscilloscope Operating Procedures
The procedures outlined in this paragraph must be read before attempting to operate the oscilloscope. As an
aid to the operation a typical operating procedure follows the description of each operating mode.
a. Oscilloscope. OS-206/GGM-15(V) Preliminary Starting Procedure.
(1) Check power and interface cable connections (fig. 2-9).
(2) Connect the oscilloscope to the correct ac power source (para 2-6).
(3) For a preliminary test of the oscilloscope set the controls as follows:
Z MARKERS switch
DISPLAY RELEASE RATE switch
VERT VOLTS (MA)/CM
TRIGGER & SWEEP SELECT switch.
0.05 to 0.5