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Model 242L Operations Manual
1.1 GLOSSARY
A - Ampere
o
C - Celsius
Component - Any electrical or electronic device
DC - Direct Current
Firmware – Program code embedded into a microcontroller unit
Hz - Hertz
IC - Integrated Circuit
Jumper - A means of connecting/disconnecting two or more conductive by soldering/desoldering a
conductive wire or by PCB post jumper
LED - Light Emitting Diode
LOGIC - Negative Logic Convention (Ground True) State
mA - milliAmpere
ms - millisecond
MCU - Micro Controller Unit or microcontroller unit
MOV - Metal Oxide Varistor
Opto-coupler – An integrated circuit that provides electrical isolation
PCB - Printed Circuit Board
RMS - Root-Mean-Square
s – second
Schmitt Circuit – a circuit that provides hysterisis in the threshold
SW – Switch
uF - microfarad
VAC - Voltage Alternating Current
VDC - Voltage Direct Current
1.2 GENERAL DESCRIPTION
The Eberle Design Model 242L is a dual channel DC Isolator unit designed to meet Caltrans
specifications TEES 2009 including Errata #2 (December 2014). 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. Outputs are optically-isolated solid-state transistors. The Model 242L is powered from the
24VDC Cabinet Power Supply and does not require AC Line.
1.3 GENERAL CHARACTERISTICS
Each channel of the Model 242L provides input hysterisis and digital filtering to qualify the input signal.
An input signal must meet the minimum pulse requirements specified in section 1.7.5 in order to
produce a valid output. The output pulse width for both channels can be set to 100 milliseconds
minimum by installing jumper "100ms" (J4-A).
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.
Eberle Design Inc.
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