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1.1 DESCRIPTION
The Eberle Design Model 242E is a dual channel DC Isolator unit designed to meet
Caltrans specifications TSCES 1989, and TEES August 2002 Chapter 1. The isolator unit
occupies one position of a 170 standard input file. The isolator unit card incorporates a
double-sided 44 pin edge connector for the connection of power, input, and output signals.
Each channel has individual front panel controls for testing the operational mode, and high
intensity front panel LEDs which are used to indicate the output state and a fault condition
on the output. Outputs are optically-isolated solid-state transistors.
1.2 ENHANCED FEATURES
The Model 242E builds on the standard DC Isolator capabilities by adding:
Additional Fault Output indicators to alert a technician to problems with the Model
242E outputs or associated Controller Unit inputs. This simplifies diagnosing problems
due to output or input circuit problems or wiring errors.
Three separate Input Pulse filter settings per channel provide a mechanism to screen
out transient input pulses that may be the result of noise conditions or signal bounce.
In some cases additional filtering can be used to ensure critical signals such as Flash
Sense are not improperly processed by the Controller Unit due to transient noise
injected into the cabinet wiring system, for example.
The polarity of the output signal can also be inverted individually for each channel.
1.3 GENERAL CHARACTERISTICS
Each channel of the Model 242E provides input hysterisis and digital filtering to qualify the
input signal. An input signal must meet the minimum pulse requirements specified in
section 1.8.5 in order to produce a valid True output.
Both the input and output circuits have been designed for maximum protection from
electrical transients. The inputs have been designed to withstand the discharge of a 10 uF
capacitor charged to +/- 1000 Vdc directly across the input pins, and a discharge of a 10 uF
capacitor charged to +/- 2000 Vdc applied through a source impedance of 5 ohms across
the input pins or to Equipment Ground. The outputs are protected by a transient clamp
diode.
The Model 242E handle assembly is made of GE Lexan
durable polycarbonate resin. The design of this assembly strengthens and protects the
whole PCB assembly much better than conventional metal face plates.
1.4 INSTALLATION AND ADJUSTMENTS
Installation of the unit consists of plugging into the appropriate slot of the Input File and
connecting the assigned inputs to the proper cabinet terminals. The edge connector is
keyed to prevent incorrect installation.
Following power-up, a front panel LED test will illuminate all indicators for two seconds.
1.4.1 OUTPUT POLARITY
If desired, the output polarity for Channel 1 and Channel 2 can each be inverted by setting
the DIP switches SW1.1 and SW1.4 marked "Polarity" to the ON position. The polarity may
also be inverted by installing optional jumpers SEL1 and SEL2 respectively.
Eberle Design Inc.
Model 242E
Operations Manual
Section 1
General
TM
Type 121, which is a super
Page 1
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