Allen-Bradley ControlLogix 1756-IF4FXOF2F User manual

Publication 1756-IN004A-EN-P - February 2002
Installation Instructions
ControlLogix
High Speed Analog I/O Module
Catalog Number 1756-IF4FXOF2F
Obtain a User Manual
This product also has a user manual (pub. no. 1756-UM005). To view
it, visit www.ab.com/manuals or www.theautomationbookstore.com.
To purchase a manual, you can:
•contact your distributor or Rockwell Automation representative
•visit www.theautomationbookstore.com and place an order
•call 800.963.9548 (USA/Canada) or 001.320.725.1574 (outside
USA/Canada)
To: See page:
Obtain a User Manual 1
Identify the ModuleComponents 6
Prevent Electrostatic Discharge 5
Note the Power Requirements 7
Install the Module 7
Key the Removable Terminal Block/Interface Module 8
Wire the Module 11
Assemble the Removable Terminal Block and the Housing 13
Install the Removable TerminalBlock onto the Module 13
Checkthe Indicators 14
Remove the Removable Terminal Block from the Module 15
Remove the Module 15
See 1756-IF4FXOF2FSpecifications 16
Spare Allen-Bradley Parts

2ControlLogix High Speed Analog I/O Module
Publication 1756-IN004A-EN-P - February 2002
Important User Information
Because of the variety of uses for the products described in this
publication, those responsible for the application and use of these
products must satisfy themselves that all necessary steps have been
taken to assure that each application and use meets all performance
and safety requirements, including any applicable laws, regulations,
codes and standards. In no event will Allen-Bradley be responsible
or liable for indirect or consequential damage resulting from the use
or application of these products.
Any illustrations, charts, sample programs, and layout examples
shown in this publication are intended solely for purposes of
example. Since there are many variables and requirements associated
with any particular installation, Allen-Bradley does not assume
responsibility or liability (to include intellectual property liability) for
actual use based upon the examples shown in this publication.
Allen-Bradley publication SGI-1.1, Safety Guidelines for the
Application, Installation and Maintenance of Solid-State Control
(available from your local Allen-Bradley office), describes some
important differences between solid-state equipment and
electromechanical devices that should be taken into consideration
when applying products such as those described in this publication.
Reproduction of the contents of this copyrighted publication, in
whole or part, without written permission of Rockwell Automation, is
prohibited.

ControlLogix High Speed Analog I/O Module 3
Publication 1756-IN004A-EN-P - February 2002
Throughout this publication, notes may be used to make you aware
of safety considerations. The following annotations and their
accompanying statements help you to identify a potential hazard,
avoid a potential hazard, and recognize the consequences of a
potential hazard:
WARNING
!
Identifies information about practices or
circumstances that can cause an explosion in a
hazardous environment, which may lead to
personal injury or death, property damage, or
economic loss.
ATTENTION
!
Identifies information about practices or
circumstances that can lead to personal injury or
death, property damage, or economic loss.
IMPORTANT
Identifies information that is critical for
successful application and understanding of the
product.
Spare Allen-Bradley Parts

4ControlLogix High Speed Analog I/O Module
Publication 1756-IN004A-EN-P - February 2002
Environment and Enclosure
ATTENTION
!
This equipment is intended for use in a Pollution
Degree 2 industrial environment, in overvoltage
Category II applications (as defined in IEC
publication 60664-1), at altitudes up to 2000 meters
without derating.
This equipment is considered Group 1, Class A
industrial equipment according to IEC/CISPR
Publication 11. Without appropriate precautions,
there may be potential difficulties ensuring
electromagnetic compatibility in other
environments due to conducted as well as radiated
disturbance.
This equipment is supplied as "open type"
equipment. It must be mounted within an
enclosure that is suitably designed for those
specific environmental conditions that will be
present and appropriately designed to prevent
personal injury resulting from accessibility to live
parts. The interior of the enclosure must be
accessible only by the use of a tool. Subsequent
sections of this publication may contain additional
information regarding specific enclosure type
ratings that are required to comply with certain
product safety certifications.
See NEMA Standards publication 250 and IEC
publication 60529, as applicable, for explanations
of the degrees of protection provided by different
types of enclosure. Also, see the appropriate
sections in this publication, as well as the
Allen-Bradley publication 1770-4.1 ("Industrial
Automation Wiring and Grounding Guidelines"),
for additional installation requirements pertaining
to this equipment.

ControlLogix High Speed Analog I/O Module 5
Publication 1756-IN004A-EN-P - February 2002
Prevent Electrostatic Discharge
Removal and Insertion Under Power
ATTENTION
!
This equipment is sensitive to electrostatic
discharge, which can cause internal damage and
affect normal operation. Follow these guidelines
when you handle this equipment:
•Touch a grounded object to discharge
potential static.
•Wear an approved grounding wriststrap.
•Do not touch connectors or pins on
component boards.
•Do not touch circuit components inside the
equipment.
•If available, use a static-safe workstation.
•When not in use, store the equipment in
appropriate static-safe packaging.
WARNING
!
When you insert or remove the module while
backplane power is on, an electrical arc can
occur. This could cause an explosion in
hazardous location installations. Be sure that
power is removed or the area is nonhazardous
before proceeding.
Spare Allen-Bradley Parts

6ControlLogix High Speed Analog I/O Module
Publication 1756-IN004A-EN-P - February 2002
Identify the Module Components
You received the following components with your order:
•1756-IF4FXOF2F module
•Removable Terminal Block (RTB) door label
If you did not receive these components, contact your local
distributor Rockwell Automation sales office.
This module mounts in a ControlLogixchassis and uses a
separately-ordered RTB or a Bulletin 1492 Interface Module (IFM) to
connect all field-side wiring.
This module uses one of the following RTBs:
•1756-TBCH 36 position Cage clamp RTB
•1756-TBS6H 36 position Spring clamp RTB
Use an extended-depth cover (1756-TBE) for applications with heavy
gauge wiring or requiring additional routing space. When using an
IFM, consult the documentation that came with it to connect
all wiring.
IMPORTANT Before you install your module, you should
have already:
•installed and grounded a 1756 chassis and
power supply.
•ordered and received an RTB or IFM and its
components for your application.

ControlLogix High Speed Analog I/O Module 7
Publication 1756-IN004A-EN-P - February 2002
Note the Power Requirements
This module receives power from the 1756 chasis power supply and
requires 2 sources of power from the backplane:
•375mA at 5.1V dc
•100mA at 24V dc
Add this current/power value (4.3W) to the requirements of all other
modules in the chassis to prevent overloading the power supply.
Install the Module
You can install or remove the module while chassis power is applied.
WARNING
!
When you insert or remove the module while
backplane power is on, an electrical arc can
occur. This could cause an explosion in
hazardous location installations. Be sure that
power is removed or the area is nonhazardous
before proceeding.
20861–M 20862–M
1. Align circuit board with top and
bottom chassis guides. 2. Slide module into chassis until module locking tabs ‘click’.
Printed
Circuit
Board
Locking tab
Spare Allen-Bradley Parts

8ControlLogix High Speed Analog I/O Module
Publication 1756-IN004A-EN-P - February 2002
Key the Removable Terminal Block/Interface Module
Use the wedge-shaped keying tabs and U-shaped keying bands to
prevent connecting the wrong wires to your module.
Key positions on the module that correspond to unkeyed positions
on the RTB. For example, if you key the first position on the module,
leave the first position on the RTB unkeyed.
Reposition the tabs to rekey future module applications.
Wire the Removable Terminal Block
Wire the RTB with a 1/8 inch (3.2mm) maximum flat-bladed
screwdriver before installing it onto the module. Shielded cable is
required when using this module.
We recommend using Belden 8761 cable to wire the RTB. The RTB
terminations can accommodate 14-22 gauge shielded wire.
WARNING
!
When you connect or disconnect the Removable
Terminal Block (RTB) with field side power
applied, an electrical arc can occur. This could
cause an explosion in hazardous location
installations. Make sure that power is removed or
the area is nonhazardous before proceeding.
20850–M
1. Insert the U-shaped bandas shown.
2. Push the banduntil it snaps in place.
U-shaped
bands
1. Insert the wedge-shaped tab with rounded edge first.
2. Push thetab until it stops.
20851–M
Wedge-shaped tab
Key the Module Key the RTB/IFM

ControlLogix High Speed Analog I/O Module 9
Publication 1756-IN004A-EN-P - February 2002
Connect grounded endof the cable
Ground one end of the cable only. Follow the steps below.
1. Prepare one end of the cable for grounding.
2. Ground the drain wire. We recommend grounding the drain
wire at the field device as shown below.
3. Connect the insulated wires to the field device.
If you cannot ground at the field device, follow these steps:
1. Prepare one end of the cable as shown in step 1.
2. Ground at an earth ground on the chassis as shown below.
3. Connect the insulated wires to the RTB.
a. Removea length
of cable jacket
from the
connecting cable.
b. Pullthefoilshield
and bare drain
wire from the
insulated wire.
c. Twistthefoilshield
and drain wire
together to form a
single strand.
d. Attachagroundlug
and apply heat
shrinktubingtothe
exit area.
20104-M
Field
Device
Drain wire
43183
20918-M
Connect the drain wire to a
chassis mounting tab.
Use any chassis mounting tab
that isdesignated asa
functional signal ground.
Chassis mounting tab
Drain wire with ground lug
4M or 5M (#10 or #12)
phillips screw and star
washer (or SEM screw)
4M or 5M (#10 or #12)
star washer
Spare Allen-Bradley Parts

10 ControlLogix High Speed Analog I/O Module
Publication 1756-IN004A-EN-P - February 2002
Connect ungrounded endof the cable
1. Prepare the non-grounded end of the cable.
2. Connect the insulated wires to:
•the RTB (as shown below) if the cable is grounded at the
field device.
or
•the field device if the cable is grounded at the chassis.
a. Remove a length
of cable jacket
from the
connecting cable.
b. Pullthefoilshield
and bare drain
wire from the
insulated wire.
c. Cutthefoilshieldanddrain
wire back to the cable
casing and apply shrink
wrap, exposing only the
insulated wires.
43182
Spring Clamp RTB Cage Clamp RTB
20860-M 20859-M
A. Strip 7/16 inch (11mm) maximumlength
of wire.
B. Insert thescrewdriver into the inner hole
of the RTB.
C. Insert the wire intothe open
terminal and remove the
screwdriver.
A. Strip 3/8 inch (9.5mm) maximumlength
of wire.
B. Insert the wire into the open terminal.
C. Turn the screw clockwise to close the
terminal on the wire.

ControlLogix High Speed Analog I/O Module 11
Publication 1756-IN004A-EN-P - February 2002
Wire the Module
You can only connect wiring to your module through an RTB or IFM.
The example below shows how to wire the module.
12 34 56
78 910
1112
1314 1516
1718 1920
2122
2324
2526 2728
2930 3132 3334
3536
+IN-1/V
IN-1/I
-IN-1
+IN-3/V
V OUT-1
IN-3/I
-IN-3
Not used
Not used
I OUT-1
RTN-1
Not used
+IN-0/V
IN-0/I
-IN-0
+IN-2/V
IN-2/I
-IN-2
1756-IF4FXOF2F Current Mode Wiring Diagram
2-Wire
Transmitter A
A
A
(+) (-) i
i
42742
Shield
ground
Current
Output
Load
Not used
Not used
Not used
Not used
Not used
Not used
VOUT-0
Not used
Not used
I OUT-0
Not used
Not used
Not used
Not used
Not used
Not used
Not used
RTN-0
= Inline field device (i.e. strip chart recorder or meter)
A
Spare Allen-Bradley Parts

12 ControlLogix High Speed Analog I/O Module
Publication 1756-IN004A-EN-P - February 2002
After completing field-side wiring, secure the wires in the strain relief
area with a cable-tie.
12
34 56
78 910 1112
1314 1516
1718 1920 2122
2324
2526 2728
2930 3132 3334
3536
1756-IF4FXOF2F Voltage Mode Wiring Diagram
User
Analog
Input
Device
(+)
(-)
42743
Shield
ground
(+)
(+)
(-)
Shield
ground
+IN-1/V
IN-1/I
-IN-1
+IN-3/V
V OUT-1
IN-3/I
-IN-3
Not used
Not used
I OUT-1
RTN-1
Not used
+IN-0/V
IN-0/I
-IN-0
+IN-2/V
IN-2/I
-IN-2
Not used
Not used
Not used
Not used
Not used
Not used
V OUT-0
Not used
Not used
I OUT-0
Not used
Not used
Not used
Not used
Not used
Not used
Not used
RTN-0

ControlLogix High Speed Analog I/O Module 13
Publication 1756-IN004A-EN-P - February 2002
Assemble the Removable Terminal Block and the Housing
Install the Removable Terminal Block onto the Module
Before installing the RTB, make certain:
•field-side wiring of the RTB has been completed.
•the RTB housing is snapped into place on the RTB.
•the RTB housing door is closed.
•the locking tab at the top of the module is unlocked.
WARNING
!
When you connect or disconnect the Removable
Terminal Block (RTB) with field side power applied, an
electrical arc can occur. This could cause an explosion in
hazardous location installations. Be sure that power is
removed or the area is nonhazardous before proceeding.
20858–M
Groove
Groove
Side edge of the RTB
Side edge of the RTB
Strain relief area
1. Align the grooves at the bottom of the housing with the side edges of the RTB.
2. Slide the RTB intothe housing until itsnaps intoplace.
20853–M 20854–M
Module
guide
RTB guides
Locking
tab
1. Alignthesideandtop,bottomRTBguideswith
the side, top and bottom module guides. 2. Pressquickly andevenly to seat the RTB on the module until the latches snap into place.
3. Slide the locking tab down to lock the RTB onto themodule.
Spare Allen-Bradley Parts

14 ControlLogix High Speed Analog I/O Module
Publication 1756-IN004A-EN-P - February 2002
Check the Indicators
The indicators show CAL status (green) and a bi-colored LED for
module "OK" (red/green).
During power up, an indicator test is done and the following occurs:
•The "OK" indicator turns red for 1 second and then turns to
flashing green if it has passed the self-test.
This completes installation of the module. Use the following
information to remove the module, if necessary.
LED
indicators: This display: Means: Take this action:
OK Steady
green light The inputs andoutputs are being multicast and in normal
operating state.
None
OK Flashing
green light 1. The module has passed internal diagnostics but is
not activelycontrolled.
2 . The controller isin
Program mode.
1. Configure themodule
with RSLogix 5000.
2. If ready, switch the
controller to Run mode.
OK Flashingred
light Previously established communication has timed out. Checkcontrollerandchassis communication
OK Steadyred
light The module must bereplaced. Replace the module.
CAL Flashing
green light The moduleis in calibration mode. None
ANALOG OUTPUT
CAL
OK
42741
ANALOG INPUT

ControlLogix High Speed Analog I/O Module 15
Publication 1756-IN004A-EN-P - February 2002
Remove the Removable Terminal Block from the Module
If you need to remove the module, you must remove the RTB first.
Before removing the module, you must remove the RTB.
Remove the Module
WARNING
!
When you insert or remove the module while
backplane power is on, an electrical arc can
occur. This could cause an explosion in
hazardous location installations. Be sure that
power is removed or the area is nonhazardous
before proceeding.
20855–M
2. Open theRTB door and pull the
RTB off the module.
1. Unlock the locking tab at the
top of the module.
42517
1. Push in top and bottom locking tabs. 2. Pull module out of the chassis.
20856–M 20857–M
Spare Allen-Bradley Parts

16 ControlLogix High Speed Analog I/O Module
Publication 1756-IN004A-EN-P - February 2002
1756-IF4FXOF2F Specifications
General Module Specifications
Module Location 1756 ControlLogix chassis
Backplane Current
(Nomodule external
power requirements)
375mA @ 5.1V dc & 100mA @ 24V dc
(Total backplane power = 4.3W)
PowerDissipation within Module
ThermalDissipation
4.3W voltage
4.7W current
14.66 BTU/hr voltage
16.02 BTU/hr current
Data Format FloatingpointIEEE 32 bit
Isolation Voltage
Field side to system side Optoisolated, transformer isolated 100% tested at 2550V dc for 1s
RTB Screw Torque (NEMA) 7-9 inch-pounds (0.8-1Nm)
Module Keying (Backplane) Electronic
RTB Keying Userdefined
Field Wiring Arm and Housing 36 Position RTB (1756-TBCH or TBS6H)(1)
Conductors Wire Size
Category
22-14 gauge (2mm2) stranded (2)
3/64 inch (1.2mm) insulation maximum
2(2)
Screwdriver Width for RTB 5/16 inch (8mm) maximum
Environmental Conditions
Operating Temperature IEC 60068-2-1 (Test Ad,Operating Cold)
IEC 60068-2-2 (Test Bd, Operating Dry Heat)
IEC 60068-2-14 (Test Nb, Operating Thermal Shock)
0 to 60°C (32 to 140°F)
Storage Temperature IEC 60068-2-1 (Test Ab,Un-packaged Non-operating
Cold)
IEC 60068-2-2 (Test Bc, Un-packaged Non-operating
Dry Heat)
IEC 60068-2-14 (Test Na, Un-packaged Non-operating
Thermal
–40 to 85°C (–40 to 185°F)
Relative Humidity IEC 60068-2-30(TestDb, Un-packaged Non-operating
Damp Heat)
5 to 95% non-condensing
Vibration IEC60068-2-6 (TestFc, Operating)
2g @ 10-500Hz

ControlLogix High Speed Analog I/O Module 17
Publication 1756-IN004A-EN-P - February 2002
Environmental Conditions (continued)
Shock IEC60068-2-27:1987, Test Ea (Unpackaged shock,
ES#002)
Operating 15g
Non-operating 30g
Emissions CISPR 11
Group 1, Class A
ESD Immunity IEC 61000-4-2
6kV contactdischarges
15kV air discharges
Radiated RF Immunity IEC 61000-4-3
10V/m with 1kHz sine-wave 80%AM from 30MHz to
2000MHz
10V/m with 200Hz 50% Pulse 100%AM at 900Mhz
EFT/B Immunity IEC 61000-4-4
±4kV at 2.5kHz on power ports
±2kV at 5kHz on signal ports
Surge Transient Immunity IEC 61000-4-5
+2kV line-earth (CM) on shielded ports
Conducted RFImmunity IEC 61000-4-6
10Vrms with1kHz sine-wave80%AM from 150kHz to
80MHz
Enclosure Type Rating None (open-style)
Certifications
(where product is marked) UL UL Listed Industrial Control Equipment CSA CSA Certified Process ControlEquipment
CSA CSA Certified Process Control Equipment
for Class I, Division 2 Group A,B,C,D
Hazardous Locations
FM FM Approved Equipment for use in Class I
Division 2 Group A,B,C,D Hazardous
Locations
CE(3) EuropeanUnion89/336/EECEMCDirective,
compliant with:
EN 50081-2; Industrial Emissions
EN 50082-2; Industrial Immunity
EN61326;Meas./Control/Lab.,Industrial
Requirements
EN 61000-6-2; Industrial Immunity
C-Tick(3) Australian Radiocommunications Act,
compliant with:
AS/NZS 2064; Industrial Emissions
Spare Allen-Bradley Parts

18 ControlLogix High Speed Analog I/O Module
Publication 1756-IN004A-EN-P - February 2002
Input Specifications
Number of Inputs 4 differential inputs
Input Range Selections +/- 10.5V, 0-10.5V, 0-5.25V, 0-21ma
overrange indication when exceeded
Voltage Resolution
+/- 10.5V range
0-10.5V range
0-5.25V range
Approximately 14 bits across +/-10.5V dc (21V total)
1.3mV/bit- 14-bit effective
1.3mV/bit- 13-bit effective
1.3mV/bit- 12-bit effective
Current Resolution
0-21ma range Approximately 12 bits across 21mA 5.25µA/bit
Repeatability +1 Least Significant Bit (LSB)(4)
Input Impedance >1MΩ- voltage
249Ω- current
Open CircuitDetection Time Positive full scale reading within 1 second
Overvoltage Protection 30V dc -whenwired for voltage operation
8V ac/dc - when wired for current operation
Common Mode Noise Rejection 70dB typical, 50/60 Hz
Accuracy at 25°C 0.05% of range immediately after calibration
Better than 0.1% of range within calibration interval
Calibration Interval 12 months typical
Gain Drift with Temperature 25 ppm/degree C maximum - voltage
35 ppm/degree C maximum - current
Input Error over Full Temp. Range 0.2% of range
MinimumScan Time for all
Channels (Sample Rate) 400µS
Input Conversion Method Successive approximation
Output Specifications
Number of Outputs 2 voltage or currentoutputs
Output Range 0 - 21mA
+/-10.4V
Resolution 13 bits across 21mA = 2.8µA/bit
14 bits across 20.8V = 1.3mV/bit
Open Circuit Detection Current output only (Output must be set to >0.1mA)
Output OvervoltageProtection 24Vdc
Output Short Circuit Protection Electronically current limited to 21mA or less
Drive Capability >2000Ω- voltage
0-750Ω- current
Output Settling Time <2mS to 95% of final value with resistive loads

ControlLogix High Speed Analog I/O Module 19
Publication 1756-IN004A-EN-P - February 2002
Accuracy at 25°C
Current (4mA to21mA range)
Voltage (-10.4 to +10.4V range)
0.05%ofselectedrangeimmediatelyaftercalibration
Better than 0.1% of range with calibration interval
Better than 0.1% of range with calibration interval
Calibration Interval 12 months typical
Output Offset Drift
with Temperature 50µV/°C typical
1µA/°C typical
Gain Drift with Temperature 25 ppm/degree C maximum - voltage
50 ppm/degree C maximum - current
Module Error over Full
Temperature Range 0.2% of range - voltage 0.3% of range- current
Min. Scan Time for allChannels 1mS
Output Conversion Method R-Ladder DAC, monotonicity with no missing codes
(1) Maximum wire size will require extended housing - 1756-TBE.
(2) Use this conductorcategory information for planning conductor routing asdescribed in the system
level installation manual. Referto publication1770-4.1 “IndustrialAutomation Wiringand Grounding
Guidelines”.
(3) See the Product Certification link at www.ab.com for Declarations of Conformity, Certificates, and
other certification details.
(4) Repeatablity is defined as the stability of the input channel reading when asteady state signal is
applied (i.e. +/- 1 LSB is one count [1.3mV] from the nominal reading).
The following information applies when operating this equipment in hazardous locations:
Productsmarked “CL I, DIV 2, GP A, B, C, D”are suitable for use in Class I Division 2 Groups A, B, C, D,
Hazardous Locationsand nonhazardous locations only. Each product is supplied withmarkings on the
rating nameplate indicating the hazardous location temperature code. When combining products within
a system, the most adverse temperature code (lowest “T”number) may be usedto help determine the
overall temperature code of the system. Combinationsof equipment in your system aresubject to
investigation by the local Authority Having Jurisdiction at the time of installation.
WARNING
!
EXPLOSION HAZARD
•Do not disconnect equipment unless power has been removed or
the area is known to be nonhazardous.
•Do not disconnect connectionsto this equipment unless power
has beenremovedor the area is known tobe nonhazardous.
Secure any external connections thatmate to thisequipment by
using screws, sliding latches, threaded connectors, or other
means provided with thisproduct.
•Substitution of components may impair suitability for Class I,
Division 2.
If thisproduct contains batteries, they must onlybe changed inan
areaknown to be nonhazardous.
Spare Allen-Bradley Parts

Publication 1756-IN004A-EN-P - February 2002 PN 957280-56
Copyright © 2002 Rockwell Automation. All rights reserved. Printed in the U.S.A.
Informations sur l’utilisation de cet équipement en environnements dangereux :
Les produits marqués "CLI, DIV 2, GP A, B, C, D" neconviennent qu’à une utilisation en environnements
de ClasseI Division 2Groupes A, B, C,D dangereux et non dangereux.Chaque produit estlivréavecdes
marquages sur sa plaque d’identification qui indiquent le code de température pour les environnements
dangereux. Lorsque plusieurs produits sont combinés dans un système, le code de température le plus
défavorable(codedetempératurele plusfaible)peutêtreutilisépourdéterminerlecodedetempérature
global du système. Les combinaisonsd’équipements dans le système sont sujettes àinspection par les
autorités locales qualifiées au moment de l’installation.
AVERTISSEMENT
!
RISQUE D’EXPLOSION
•Couper le courant ou s’assurer que l’environnement est classé
non dangereux avant de débrancher l'équipement.
•Couperle courant ou s'assurer que l’environnement est classé
non dangereux avant de débrancher lesconnecteurs. Fixer tous
les connecteurs externes reliés àcet équipement àl'aide de vis,
loquetscoulissants,connecteursfiletésouautresmoyensfournis
avec ce produit.
•La substitution de composants peut rendre cet équipement
inadaptéàune utilisationen environnement de ClasseI,Division
2.
S’assurer que l’environnement est classénon dangereux avant de
changer les piles.