USSI Microlok II Functional description
Page 14 of 27 July 2005 UM-6800A Rev1.3
Fig. 5 Ref
Label
Device
Purpose
1
OUT1 -OUT8
Yellow LEDs
Monitor state of vital outputs 1 through 8. When lit,
indicates respective output is turned on.
2
OUT9 -OUT16
Yellow LEDs
Monitor state of vital outputs 9 through 16. When lit,
indicates respective output is turned on.
Vital Outputs
The Vital Outputs are designed primarily to interface with vital relays. In
typical railway and transit applications, most Vital relays are specified to use
nominal 24V DC supply voltage.
•
The minimum voltage for a Vital Output in the ON state will be 95% of I/O
supply battery for 24V DC outputs.
•
The maximum voltage for a Vital Output in the OFF state will be such that
a Vital relay will not remain picked at the current produced. This voltage
is 1.5V DC for a 24V DC output.
•
The output will be capable of driving a minimum output load of 100
Ω
for
the 24V DC outputs.
Control of outputs
Each output is controlled by the processor and monitored by a circuit
providing feedback to the processor to ensure that the output is indeed what
was requested by processor. Also, to check the integrity of the feedback loop,
the outputs are cycled on a periodic basis. If an output is currently turned
on, the processor will turn it off for an instant and verify the correct response
from the monitor. Failure of these checks would result in a system shutdown
and reset. See the figure-1.
Vital Input Board
There are no power connections required through the upper connector. When
wiring a vital input PCB to a relay contact circuit contained in the same
house of the Microlok II card file, the signal battery may be used as the
energy source to activate the inputs. Terminals designated (-) may be
connected to battery N24 and B24 switched over relay contacts. When wiring
a vital input PCB to a relay contact circuit outside the Microlok II house, use
the isolated source that is part of the power supply. This is consistent with
the practice of confining signal battery to the case in which the Microlok II
unit is housed.
•
Each Vital Input PCB is having 16 Inputs.
•
Each input is assigned to the detection of outdoor gear status such as
ECRs in case of signal, WKR incase of points & TPR in case of Track.
