889-3809-00
Model 2018 Operations Manual Rev Apr 2020 Page
3
of 41
Section 2
General Characteristics
The Model 2018 monitor was designed to meet and/or exceed the specifications in Chapter 3 Section 6 of the
Caltrans Transportation Electrical Equipment Specifications (TEES) dated 08/16/02. The Model 2018 monitor
includes several features designed to enhance the safety and operation of the monitor. These features extend the
Model 2018 monitor features beyond the requirements of the Caltrans standards.
2.1
INPUTS
2.1.1
AC LINE ( AC + )
The over-current protected side of 120-volt AC 60 Hz source. This input (Rear Edge Connector - Pin FF) is used
to generate the voltages required to operate the monitoring logic.
The monitor has a printed circuit board mounted over-current protection device in the 120-volt AC input to the
unit. This fuse is a 1/4 AMP SLO-BLOW and should only be replaced with a fuse of the same type and value.
Typical Connection: Cabinet AC Line power source.
2.1.2
AC NEUTRAL ( AC - )
The un-fused and un-switched return side of 120-volt AC 60 Hz power source is taken from the neutral output of
the AC power source. This input (Rear Edge Connector - Pin 21) is the referenced signal for all field terminal
voltage sensing inputs. This input is not connected to Logic Ground or Earth Ground within the unit.
Typical Connection: Cabinet AC Neutral.
2.1.3
EARTH GROUND
The monitor has an input terminal (Rear Edge Connector - Pin U) providing an independent connection to the
chassis of the unit. This input is not connected to DC Ground or AC Neutral within the unit.
Typical Connection: Cabinet Earth Ground.
2.1.4
FIELD TERMINALS (REDS, YELLOWS, AND GREENS)
The monitor has 54 field terminal inputs (18 Greens, 18 Yellows, and 18 Reds). 38 of these inputs are through the
Rear Edge Connector (Channel 1-18 Greens, Channel 1-18 Yellows, and Channel 17 and 18 Reds). The other 16
inputs are through the front panel Red Interface Connector (Channel 1-16 Reds).
Each field terminal input is measured approximately 13,000 times per second to provide an accurate, true RMS
(root mean square) AC voltage regardless of distortions in the waveform or changes in line frequency. Both
positive and negative half wave rectified signals are sensed. The RMS voltage is calculated over the last two
cycles of the line power (approximately 33 milliseconds) every cycle of the line power for every AC input.
Voltages can be accessed in real-time via the serial port and are recorded in the Signal Sequence Log if a fault
occurs.
Three inputs are provided for each channel to permit the monitoring of voltages at the Green / Walk, Yellow, and
Red / Don’t Walk signal field terminals.
In the Incandescent Mode (Incandescent Field Displays):
A Green or Yellow signal input is sensed as ON when it exceeds 25V
RMS
and a signal input is sensed
as OFF when it is less than 15V
RMS
. Signals between 15V
RMS
and 25V
RMS
may be in either state.
A Red signal input is sensed as ON when it exceeds 70V
RMS
and a signal input is sensed as OFF when
it is less than 50V
RMS
. Signals between 50V
RMS
and 70V
RMS
may be in either state.
In the LED mode (LED Field Displays):
For the purpose of testing for Conflicts, Multiple Indications, Flashing Don’t Walk Monitoring, and
ensuring that channels 17 and 18 are OFF when a 16-channel program card is used, a Green, Yellow,
or Red signal input is sensed as ON when it exceeds 25V
RMS
and a signal input is sensed as OFF when
it is less than 15V
RMS
. Signals between 15V
RMS
and 25V
RMS
may be in either state.
For the purpose of testing for Red Fails, Co-Channel Childs, Short Yellows, and Short Clearance, a
Green, Yellow, or Red signal input is sensed as ON when it exceeds 70V
RMS
and a signal input is
sensed as OFF when it is less than 50V
RMS
. Signals between 50V
RMS
and 70V
RMS
may be in either
state.