Table of Contents
Advertisement
CHAPTER 3
ATTENUATORS AND FEEDBACK LIMITERS
3.1
ATTENUATORS
3.1.1
Introduction
The 580 Computers have provisions for 10 handset attenuators (Figure 3.la) and
70 servo set attenuators (Figure 3.lb) when fully expanded.
Each row of atten-
uators (one row of handset attenuators and seven rows of servo set attenuators)
is terminated in a particular field on the patch panel.
The first digit in the
attenuator address indicates the field number.
For example, the handset atten-
uators are all
terminated in FIELD 0 and are numbered 00 through 09.
Each row
of the seven rows of servo set attenuators is terminated in a particular field.
With the exception of the ungrounded attenuator in each _4 position, all atten-
uators in a particular field have one end internally grounded with the ungrounded
end and the wiper terminated on the patch panel.
The ungrounded pot in each
field has both ends and the wiper terminated on the patch panel.
The standard potentiometers are ten-turn, wirewound, 5000 ohm units.
The handset
attenuators are equipped with vernier
di~ls
that have a locking mechanism.
3.1.2
Grounded Attenu_ators
Figure 3.2a shows the circuits used in the 580 for setting grounded attenuators
under load.
Relay·Kl is energized when the cdmputer is placed in set pot mode
and applies reference voltage to the high end of all grounded attelluators.
Re-
lay K2 is energized when the attenuator is addressed by the signal selector
system.
The wiper voltage is connected to the input of the DVM.
The wiper is
still connected to the patch panel and is patched to the load it sees when in
use.
The wiper of the attenuator is adjusted until the desired coefficient is
obtained on the DVM.
3.1.3
Ungrounded Attenuators
The operation of the ungrounded attenuators (Figure 3.2b) is similar to the
grounded attenuators except that the lower terminal is not internally grounded.
Prior to setting an ungrounded attenuator, the lower terminal must be patched
to ground.
If setting is attempted without the ground connection, the servo
drives the attenuator to its highest resistance.
The attenuator is held in
this position until the CLR pushbutton is depressed and the attenuator is
grounded.
The ground can be removed from the attenuator once it is set and
its address removed.
3Q2
FEEDBACK LIMITER
3.2.1
General
Feedback Limiter, Model 0.42.0342 provides three variable and accurate feed-
back limiters capable of limiting either or both the positive and negative
amplifier outputs.
3-1
Advertisement
Table of Contents
