Vital Relays and Timers
Ansaldo STS USA
(Formerly known as Union Switch & Signal)
RSE-4H2
Rev. 3-09
PN-250F Solid-State Flasher Relay
(Replacement for ASTS USA PF-256 Relay)
The new PN-250F Solid-State Flasher relay
replaces ASTS USA’s PF-256 unit, providing the
same high level of reliability in railroad flashing
light applications, but with a variety of design and
service improvements. Among these are allelectronic control of the flash rate, two flash rate
settings in one relay, and greatly improved
contact and armature assembly designs.
General Description
The PN-250F is as biased relay that features an
internally-mounted electronic flasher module to
operate the relay; this is the same highly reliable
module as used in the PN-150F. Since the flash rate
is electronically controlled, the rate is no longer
dependent on mechanical adjustments. Unlike the
PF-256F, the PN-250F provides both 45 flashes per
minute (FPM) and 60 FPM options in the same relay.
The rate is easily changed via a 7” (17.78 cm) jumper
on the rear of the existing relay base (45 FPM with
jumper installed, 60 FPM without jumper).
The PN-250F incorporates four normal and four
reverse contacts using silver alloy-to-silver alloy.
These contacts are far superior to the contacts used
in the older PF-256. In addition, the armature
assembly is hinged, eliminating the pivot screws and
the wear associated with pivots of previous flasher
relays. The DC-attractive armature is energized by
one 87.5 ohm coil. For highway crossing light
operation, contact open and close times are equal
and slightly less than 50% of the total cycle; this
ensures there are periods where both lights are dark.
The PN-250F relay provides ordinary pick-up and
dropaway values as a standard biased relay.
Checking of the electrical calibration values is
accomplished with a wire terminated to bypass the
internal flasher module. DC calibration tests are
accomplished by connecting +battery to 1B, and –
battery to 1F. This allows calibration to be measured
without opening the relay.
To order, call 1-800-652-7276
e-mail: orders@ansaldo-sts.us
Advantages
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Highly dependable flash rate from solid-state
module
Mechanical rate adjustments eliminated
Greatly improved contacts and armature assembly
One relay for all standard flash rate applications
Simple jumper selection of flash rate
Direct replacement for PF-256; no circuit rewiring
Application
The PN-250F is designed for 8 to 15 volt systems and
serves all railway flashing light circuit applications
previously served by the PF-256 electro-mechanical
relay. Highway crossing flashing light systems
typically use the 45 FPM rate, while flashing wayside
signals typically use the 60 FPM rate.
The new relay is a direct plug-in replacement for the
PF-256F (part number series N322561-XXX). No
wiring changes are required to the existing PF-256F
circuits when retrofitting with the PN-250F. Relay
base wiring is exactly the same as the PF-256. Wiring
terminations for the old style Bakelite base terminal
are +A(+) and –A(-), while the new style base
terminations are 1A(+) and 1F(-). Indexing is
arranged so that the PN-250F can fit into either the
PF-256-001(45-55) or the –002 (55-65) base.
www.ansaldo-sts.com
RSE-4H2, p. 1
Ansaldo STS USA
(Formerly known as Union Switch & Signal)
PN-250F Solid-State Flasher Relay
(Replacement for ASTS USA PF-256 Relay)
RSE-4H2
Rev. 3-09
Specifications
Ordering Information
Coil Resistance:
87.5 Ohms
Energization:
0.26A
Drop-Away:
0.024A
Full Drop-Away:
0.006A
Pick-Up and Working:
0.065A
System Voltage:
10 to 15 Vdc
Opt. On-Time Rate:
Calibrated at 12 Vdc.
Contacts:
4N, 4R silver alloy-to-silver
alloy
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Refer to ordering tabulation below for PN-250F
part number.
Refer to RSE-4S1 for shop maintenance tools
and supplies.
Request ASTS USA Service Manual SM-9080 for
additional information.
5A (30 Vdc) or 175 Vac.
Flash Rates:
45 or 60 FPM
Temp. Range:
-40°C to +70°C (-40°F to
+158°F)
Order No. PN-250F SS Flasher Relay
N40116101 PN-250F Solid-State Flasher Relay (complete)
RSE-4H2, p. 2