Tektronix MTM400A Use and care manual

xx
MTM400A, IPM400A, and RFM300
DTV Monitors
Specifications and Performance Verification
ZZZ
Technical Reference
*P077017602*
077-0176-02

MTM400A, IPM400A, and RFM300
DTV Monitors
Specifications and Performance Verification
ZZZ
Technical Reference
xx
This document applies to firmware versions 4.0 and above.
www.tektronix.com
077-0176-02

Copyright © Tektronix. All rights reserved. Licensed software products are owned by Tektronix or its subsidiaries
or suppliers, and are protected by national copyright laws and international treaty provisions.
Tektronix products are covered by U.S. and foreign patents, issued and pending. Information in this publication
supersedes that in all previously published material. Specifications and price change privileges reserved.
TEKTRONIX and TEK are registered trademarks of Tektronix, Inc.
FlexVuPlus is a registered trademarks of Tektronix, Inc.
Contacting Tektronix
Tektronix, Inc.
14200 SW Karl Braun Drive
P.O. Box 500
Beaverton, OR 97077
USA
For product information, sales, service, and technical support:
In North America, call 1-800-833-9200.
Worldwide, visit www.tektronix.com to find contacts in your area.

Table of Contents
General Safety Summary ......................................................................................... iv
Preface............................................................................................................. vii
Product Documentation..................................................................................... vii
Specifications ....................................................................................................... 1
Electrical, Hardware, and Signal Specifications............................................................ 1
Power Source Characteristics................................................................................ 15
Environmental Characteristics .............................................................................. 16
Mechanical (Physical) Characteristics...................................................................... 16
Performance Verification ......................................................................................... 17
Requirements.................................................................................................. 17
Procedure ...................................................................................................... 17
MTM400A, IPM400A, and RFM300 Specifications and Performance Verification i

Table of Contents
List of Figures
Figure 1: DTV monitor RUI display ............................................................................ 18
ii MTM400A, IPM400A, and RFM300 Specifications and Performance Verification

Table of Contents
List of Tables
Table i: Product documentation................................................................................. vii
Table 1: Remote User Interface (RUI) platform characteristics............................................... 1
Table 2: TS processor card - system timing clock .............................................................. 1
Table 3: TS processor card - ASI interface...................................................................... 1
Table 4: TS processor card - SMPTE310M interface ............... ........................................... 2
Table 5: TS processor card - alarm connector................................................................... 3
Table 6: TS processor card - alarms.............................................................................. 4
Table 7: TS processor card - LTC connector .................................................................... 4
Table 8: TS processor card - Ethernet RJ-45 connector........................................................ 4
Table 9: QAM Annex A interface card characteristics......................................................... 5
Table 10: QAM Annex B2 interface card characteristics...................................................... 5
Table 11: QAM Annex B2 measurements....................................................................... 5
Table 12: QAM Annex C interface card characteristics........................................................ 6
Table 13: 8PSK/QPSK interface card characteristics with 8PSK input ...................................... 6
Table 14: 8PSK/QPSK interface card characteristics with QPSK input...................................... 7
Table 15: 8PSK and QPSK measurements ...................................................................... 7
Table 16: DVB-S2 interface card characteristics ............................................................... 8
Table 17: DVB-S2 measurements ................................................................................ 8
Table 18: 8VSB interface card characteristics .................................................................. 9
Table 19: 8VSB measurements ................................................................................... 9
Table 20: COFDM interface card characteristics .............................................................. 11
Table 21: COFDM measurements............................................................................... 11
Table 22: GigE interface card - general characteristics ....................................................... 13
Table 23: GigE interface card - Ethernet electrical port....................................................... 13
Table 24: GigE interface card - Ethernet Optical port......................................................... 13
Table 25: GigE interface card - ASI input...................................................................... 14
Table 26: GigE interface card - ASI output (active loopthrough of ASI/SMPTE input or TS from GigE
interface card)................................................................................................. 14
Table 27: GigE interface card - SMPTE310M input (loopthrough to ASI output)........... .............. 15
Table 28: AC power source characteristics..................................................................... 15
Table 29: Transport stream card batteries....................................................................... 15
Table 30: Environmental characteristics........................................................................ 16
Table 31: Mechanical characteristics............................................................................ 16
MTM400A, IPM400A, and RFM300 Specifications and Performance Verification iii

General Safety Summary
General SafetySummary
Review the following safety precautions to avoid injury and prevent damage to
this product or any products connected to it.
To avoid potential hazards, use this product only as specified.
Only qualified personnel should perform service procedures.
To Avoid Fire or Personal
Injury
Use Proper Power Cord. Use only the power cord specified for this product and
certified for the country of use.
Ground the Product. This product is grounded through the grounding conductor
of the power cord. To avoid electric shock, the grounding conductor must be
connected to earth ground. Before making connections to the input or output
terminals of the product, ensure that the product is properly grounded.
Observe All Terminal Ratings. To avoid fire or shock hazard, observe all ratings
and markings on the product. Consult the product manual for further ratings
information before making connections to the product.
The inputs are not rated for connection to mains or Category II, III, or IV circuits.
Power Disconnect. The power cord disconnects the product from the power source.
Donotblockthepowercord;itmustremain accessible to the user at all times.
Do Not Operate Without Covers. Do not operate this product with covers or panels
removed.
Do Not Operate With Suspected Failures. If you suspect that there is damage to this
product, have it inspected by qualified service personnel.
Avoid Exposed Circuitry. Do not touch exposed connections and components
when power is present.
Use Proper Fuse. Useonlythefusetypeandratingspecified for this product.
Do Not Operate in Wet/Damp Conditions.
Do Not Operate in an Explosive Atmosphere.
Keep Product Surfaces Clean and Dry.
Provide Proper Ventilation. Refer to the manual’s installation instructions for
details on installing the product so it has proper ventilation.
iv MTM400A, IPM400A, and RFM300 Specifications and Performance Verification

General Safety Summary
Terms in this Manual These terms may appear in this manual:
WARNING. Warning statements identify conditions or practices that could result
in injury or loss of life.
CAUTION. Caution statements identify conditions or practices that could result in
damage to this product or other property.
Symbols and Terms on the
Product
These terms may appear on the product:
DANGER indicates an injury hazard immediately accessible as you read
the marking.
WARN ING indicates an injury hazard not immediately accessible as you
read the marking.
CAUTION indicates a hazard to property including the product.
The following symbol(s) may appear on the product:
MTM400A, IPM400A, and RFM300 Specifications and Performance Verification v

General Safety Summary
vi MTM400A, IPM400A, and RFM300 Specifications and Performance Verification

Preface
This manual contains the following information about the MTM400A, IPM400A,
andRFM300DTVMonitors:
Specifications lists the electrical, physical, and environmental specifications
of the DTV monitors.
Performance Verification contains a procedure to verify that the DTV
monitors is operating normally.
Product Documentation
Table i lists the product documentation supporting the DTV monitor.
Table i: Product documentation
Item (Tektronix part number) Purpose Location
MTM400A DTV Monitor Quick Start
User Manual (071-2492-xx English,
071-2493-xx Japanese 071-2632-xx
German)
Provides installation and high-level
operational overviews
IPM400A DTV Monitor Quick Start User
Manual (071-2698-xx English)
Provides installation and high-level
operational overviews
RFM300 DTV Monitor Quick Start User
Manual (071-2700-xx English)
Provides installation and high-level
operational overviews
MTM400 and MTM400A RUI v3.x
Upgrade Technical Reference
(077-0174-xx)
Describes the remote user interface
(RUI) changes introduced with the
MTM400A monitor
MTM400A, IPM400A, and RFM300
Technical Reference (077-0175-xx)
Provides in-depth operating information
MTM400A, IPM400A, and RFM300
Specifications and Performance
Verification Technical Reference
(077-0176-xx)
Provides complete product
specifications and a procedure
for verifying the operation of the
instrument (this document)
MTM400A, IPM400A, and RFM300 Read
This First (071-2654-xx)
Describes late breaking product
information and operational issues
MTM400A, IPM400A, and RFM300
Test Parameter and Configuration File
Technical Reference (077-0177-xx)
Provides information about using test
parameters and configuration files
MTM400A, IPM400A, and RFM300
Programmer Manual (077-0178-xx)
Provides information about remote
command syntax
MTM400A, IPM400A, and RFM300 Specifications and Performance Verification vii

Preface
Table i: Product documentation (cont.)
Item (Tektronix part number) Purpose Location
MTM400A, IPM400A, and RFM300
Declassification and Security Instructions
(077-0179-xx)
Provides instructions for removing
your proprietary information from the
instrument
MTM4UP Upgrade Instructions
(075-0973-xx)
Provides instructions for upgrading the
MTM400A DTV Monitor
IPM4UP Upgrade Instructions
(075-0997-xx)
Provides instructions for upgrading the
IPM400A DTV Monitor
RFM3UP Upgrade Instructions
(075-0993-xx)
Provides instructions for upgrading the
RFM300 DTV Monitor
viii MTM400A, IPM400A, and RFM300 Specifications and Performance Verification

Specifications
This section lists the electrical, environmental, and physical specifications of
the DTV monitors. All specifications are guaranteed unless labeled typical.
Typical specifications are provided for your convenience and are not guaranteed.
Electrical characteristics apply to test systems operating within the environmental
conditions.
Electrical, Hardware, and Signal Specifications
Table 1: Remote User Interface (RUI) platform characteristics
Characteristic Description
Minimum Specification 1.2 GHz Intel Pentium Processor (Preferred: 2 GHz)
Operating System Microsoft Windows operating systems Windows 2000, Windows XP, and Windows Vista
(Recommended: Windows XP Pro)
Disk Space 2GBfre
e disk space
Ethernet 10/100-base T
Installed Software Microsoft Internet Explorer, Version 7.0 minimum; Sun Java Runtime Environment Version
6 Update 3 minimum (1.6.0_10)
RAM 1GB
CD-ROM Drive 8x
Display 1024 x 768 pixel video monitor with 16 bit (65000) available colors
Table 2: TS processor card - system timing clock
Characteristic Description
PCR Offset Measurement Accuracy ± 2.0 ppm
System Timing Clock Drift ± 1.0 ppm per year (maximum)
Table 3: TS processor card - ASI interface
Characteristic Description
ASI Input
Connector BNC
Transport Stream Rate 155 Mbps maximum, 250 kbps minimum
Data Format Accepts both Burst and Packet mode ASI format
Signal Amplitude 2.0 Vp-p maximum; 200 mVp-p minimum
Termination 75 Ωnominal, transformer coupled
Return Loss 10 dB min, 5 MHz to 270 MHz
Link Rate 270 Mbaud ± 100 ppm
MTM400A, IPM400A, and RFM300 Specifications and Performance Verification 1

Specifications
Table 3: TS processor card - ASI interface (cont.)
Characteristic Description
ASI Output (The Output is an active loopthrough of the Input.)
Connector BNC
Impedance 75 Ωnominal, transformer coupled
Transport Stream Rate Same as the ASI input
Signal Amplitude 1.0 Vp-p max, 600 mVp-p min, into a 75 Ωload
Return Loss 10 dB min at 270 MHz
Table 4: TS processor card - SMPTE310M interface
Characteristic Description
SMPTE310M Input
Connector BNC
Termination 75 Ω, transformer coupled
Data Format Bi-phase coded. Compliant with SMPTE310M
Input Bit Rate 19,392,658.5 bps ± 2.8 ppm
Signal Amplitude 2.0 Vp-p maximum, 200 mVp-p minimum
Return Loss 10 dB min at 20 MHz
SMPTE310M Output (The Output is an active loopthrough of the Input.)
Connector BNC
Output Bit Rate Same as the SMPTE310M input
Signal Amplitude 600 mV min, 1.0 V max, into a 75 Ωload
Output Impedance 75 Ω, transformer coupled
Return Loss 10 dB min at 20 MHz
2 MTM400A, IPM400A, and RFM300 Specifications and Performance Verification

Specifications
Table 5: TS processor card - alarm connector
26-Pin, D-type connector Pin Function Description
1DGND Ground
2 TTL02 TTL Output 2
3DGND Ground
4 P5V 5 V
5RL1NC Relay 1: Normally closed contact
6RL2NC Relay 2: Normally closed contact
7RL3NC Relay 3: Normally closed contact
8RL4NC Relay 4: Normally closed contact
9RL5NC Relay 5: Normally closed contact
10 DGND Ground
11 DGND Ground
12 TTL03 TTL Output 3
13 P5V 5 V
14 RL1CC Relay 1: Common contact
15 RL2CC Relay 2: Common contact
16 RL3CC Relay 3: Common contact
17 RL4CC Relay 4: Common contact
18 RL5CC Relay 5: Common contact
19 TTL01 TTL Output 1
20DGND Ground
21TTLI1 TTL Input 1
22 RL1NO Relay 1: Normally open contact
23 RL2NO Relay 2: Normally open contact
24 RL3NO Relay 3: Normally open contact
25 RL4NO Relay 4: Normally open contact
26 RL5NO Relay 5: Normally open contact
Connector shell - Chassis ground
MTM400A, IPM400A, and RFM300 Specifications and Performance Verification 3

Specifications
Table 6: TS processor card - alarms
Characteristic Value
Alarm Relay
Number of relays 5
Maximum Switching Current 1Amp
Maximum Switch Voltage 24 VDC
Contact Resistance 100 milli-Ωmax
TTL Output Pins of the Alarms
Output Connector
Output Type TTL open collector, requires external pull-up resistor
Logic High Voltage 2.0 V min
Logic Low Voltage 0.8 V max, sinking 100 mA
Maximum Switching Current 100 mA
TTL Input Pins of the Alarms Output
Connector
Maximum Input Voltage 5.1 V
Logic High Input Voltage 2.0 V min
Logic Low Input Voltage 0.8 V max
+5 V Output, Pins 4 and 13 of the
Alarms Output Connector
Output Voltage 4.9 V min, 5.1 V max, no load
Maximum Output Current 100 mA
Output Protection Fused, self resetting
Table 7: TS processor card - LTC connector
LTC 2-pin connector Pin Function Description
1IN+
2IN-
Connector shell - Chassis ground
Port Specification
Type Linear time code, SMPTE standard to ANSI/SMPTE 12M - 1995
Input Voltage 2.0 V p-p differentially minimum
Table 8: TS processor card - Ethernet RJ-45 connector
Characteristic Description
Connector 10/100 Base-T; RJ-45 Use only good quality screened cable; Cat 6
4 MTM400A, IPM400A, and RFM300 Specifications and Performance Verification

Specifications
Table 9: QAM Annex A interface card characteristics
Characteristic Description
Input Frequency Range 51 MHz to 858 MHz, 62.5 kHz steps
Modulation Format 16 QAM, 64 QAM, 256 QAM (compliant with DVB-C ETS 300 421)
Modulation Baud Rate, QAM A 5.0 Mbaud/s minimum, 6.952 Mbaud/s maximum
Input Signal Level -57 dBm (50 dBuV) to -27 dBm (80 dBuV), with a 16, 64, and 256 QAM input, providing five or
fewer Transport Error Flags in 10 seconds, which corresponds to a post FEC rate of 1e-8
Modulation Error Ratio (with
equalizer)
38 dB min, with a 64 QAM input and 256 QAM input
Receiver Bandwidth, QAM A 8 MHz nominal
Input Termination Impedance 75 Ωnominal
Input Return Loss 6 dB min, 10 dB typical, 51 MHz to 858 MHz
Loop Through Power Gain 1.5 dB to 4 dB typical, 51 MHz to 858 MHz typical
Loop Through Noise Figure 8dBtyp
ical
Loop Through Output Return Loss Greaterthan10dBtypical
Table 10: QAM Annex B2 interface card characteristics
Characteristic Description
Input Frequency Range 88 MHz to 858 MHz
Input Signal Level -64 dBm to -19 dBm (45 dBuV to 90 dBuV relative to 75 Ω) (With either a 64 or 256 QAM
input, there are five or fewer Transport Error Flags in 11 seconds, which corresponds to a post
FEC rate of 1e-8)≥-55 dBm to ensure compliance to EN 55103-2 immunity
Modulation Format 64 QAM, 256 QAM (compliant with ITU J-83 Annex B)
Interleaving Mode Level 1 and Level 2 interleaving support compliant with all ITU J-83 Annex B, excluding I, J =
(128,7) and (128,8), and in 256 QAM excluding (8, 16) and (16, 8)
Modulation Baud Rate 64 QAM: 5.056941 Mbaud/s 256 QAM: 5.360537 Mbaud/s
Spectrum Polarity Demodulates both Normal and Inverted IF Spectrum.
Receiver Bandwidth, QAM B 6 MHz nominal
Connector Type Ftype
Input Termination Impedance 75 Ωnominal
Input Return Loss 5 dB typical
Ultimate Modulation Error Ratio
with Equalizer
≥37 dB with equalizer; typical
Table 11: QAM Annex B2 measurements
Characteristic Description
RF Lock RF lock is indicated by LED and Status
Input Level (Signal Strength)
(Typical)
Range: -64 dBm to -19 dBm (45 dBuV to 90 dBuV relative to 75 Ωs)
Resolution: 1 dB
Accuracy: ± 3 dB
MTM400A, IPM400A, and RFM300 Specifications and Performance Verification 5

Specifications
Table 11: QAM Annex B2 measurements (cont.)
Characteristic Description
EVM (Error Vector Magnitude)
(Typical)
Display Range for 64 QAM: ≤1% to ≥5% rms
Display Range for 256 QAM: ≤1% to ≥2.5% rms
Resolution: 0.1%
Accuracy: "1%
MER (Modulation Error Ratio) with
Equalizer (Typical)
Display Range:
64 QAM: 22 dB to 37 dB
256 QAM: 28 dB to 37 dB
Resolution: 0.1 dB
Accuracy:±1dBforMER<25dB;(plus-min)3dBforMER25dBto34dB
(measured at -30 dBm input)
SNR (Signal to Noise Ratio)
(Typical)
Display Range:
64 QAM: 22 dB to 37 dB
256 QAM: 28 dB to 37 dB
Resolution: 1 dB
Accuracy: "1 dB for SNR < 25 dB; ± 3 dB for SNR 25 dB to 34 dB
BER (Bit Error Ratio) Pre-RS BER is displayed
TEF (Transport Error Flag) Transport Error Flags (uncorrectable error count) ina1secondwindow and 10 second window
are displayed.
Constellation The RF constellation is displayed.
Table 12: QAM Annex C interface card characteristics
Characteristic Description
Input Frequency Range 88 MHz to 858 MHz, 62.5 kHz steps
Modulation Format 16 QAM, 64 QAM, 256 QAM (compliant with ITU J-83 Annex C)
Modulation Baud Rate, QAM C 4.5 Mbaud/s min; 5.5 Mbaud/s max
Input Signal Level -57 dBm (50 dBuV) to -27 dBm (80 dBuV), with a 16, 64, and 256 QAM input, providing five or
fewer Transport Error Flags in 12 seconds, which corresponds to a post FEC rate of 1e-8
Modulation Error Ratio (with
equalizer)
38 dB typical, with a 64 QAM input
Receiver Bandwidth, QAM C 6 MHz nominal
Input Termination Impedance 75 Ωnominal
Input Return Loss 6 dB min, 10 dB typical, 88 MHz to 858 MHz
Table 13: 8PSK/QPSK interface card characteristics with 8PSK input
Characteristic Description
Input Frequency Range 950 MHz to 2150 MHz with 1 MHz step size
Input Signal Amplitude Range -60 dBm to -30 dBm for a CBER of <1e-6
Modulation Format QPSK in accordance with ETSI EN 300 421
Modulated Baud Rate 1 MBaud min, 30 MBaud max
Turbo Viterbi Values Supported 2/3, 3/4 (2.05), 3/4 (2.1), 5/6, 8/9
6 MTM400A, IPM400A, and RFM300 Specifications and Performance Verification

Specifications
Table 13: 8PSK/QPSK interface card characteristics with 8PSK input (cont.)
Characteristic Description
Turbo FEC Turbo code
Connector Style F-style
Input Termination Impedance 75 Ωnominal
Input Return Loss 4 dB min, 950 MHz to 2050 MHz typical
LNB Supply Voltage Selectable; 13.0 V ± 1.5 V or 18.0 V (plus-min) 1.5 V, with 100 Ω, 5 watt resistor load
LNB Supply Maximum Current 200 mA maximum
LNB 22 kHz Signaling Frequency 17.6 kHz min, 26.4 kHz max (22 kHz ± 20%)
LNB 22 kHz Signaling Amplitude 600 mV p-p with 100 Ωload
Ultimate Modulation Error Ratio
(with equalizer)
26 dB with equalizer
Table 14: 8PSK/QPSK interface card characteristics with QPSK input
Characteristic Description
Input Frequency Range 950 MHz to 2150 MHz with 1 MHz step size
Input Signal Amplitude Range -60 dBm to -30 dBm for a CBER of <1e-6
Modulation Format QPSK in accordance with ETSI EN 300 421
Modulated Baud Rate 1 MBaud min, 30 MBaud max
Viterbi Values Supported 1/2, 2/3, 3/4, 5/6, 6/7, 7/8
FEC In accordance with ETSI EN 300 421
Turbo Viterbi Values Supported 1/2, 2/3, 3/4, 5/6, 7/8
Turbo FEC Turbo code
Connector Style F-style
Input Termination Impedance 75 Ωnominal
Input Return Loss 4 dB min, 950 MHz to 2050 MHz typical
LNB Supply Voltage Selectable; 13.0 V ± 1.5 V or 18.0 V (plus-min) 1.5 V, with 100 Ω, 5 watt resistor load
LNB Supply Maximum Current 200 mA maximum
LNB 22 kHz Signaling Frequency 17.6 kHz min, 26.4 kHz max (22 kHz ± 20%)
LNB 22 kHz Signaling Amplitude 600 mV p-p with 100 Ωload
Ultimate Modulation Error Ratio
(with equalizer)
26 dB with equalizer
Table 15: 8PSK and QPSK measurements
Characteristic Description
RF Lock RF lock is indicated by LED and Status.
Input Level (Signal Strength) Range: -60 dBm to -30 dBm; Resolution: 1 dBm; Accuracy: ± 5 dBm; typical
MTM400A, IPM400A, and RFM300 Specifications and Performance Verification 7

Specifications
Table 15: 8PSK and QPSK measurements (cont.)
Characteristic Description
EVM (Error Vector Magnitude) Display Range: ≤4.0% to ≥30.0% rms;
Resolution: 0.1%;
Accuracy: ± 20% of reading; typical
MER (Modulation Error Ratio) with
Equalizer
Display Range: 10 dB to 26 dB with equalizer;
Resolution: 1 dB;
Accuracy: ± 2 dB for range 10 dB to 20 dB; typical
SNR (Signal to Noise Ratio) Display Range: 5 dB to 35 dB; Resolution: 1 dB;
Accuracy: ± 2 dB for range from 5 dB to 30 dB; typical
Pre Reed Solomon (RS) BER (Bit
Error Rate)
Pre-RS BER is displayed.
Post RS BER and TEF (Transport
Error Flag)
Post Reed Solomon BER (TEF ratio), TEF rate, and number of Transport Error Flags (TEF
count) are displayed.
Constellation The RF constellation is displayed.
Table 16: DVB-S2 interface card characteristics
Characteristic Description
Input Frequency Range 950 MHz to 2150 MHz with 1 MHz step size
Input Signal Amplitude Range -60 dBm to -30 dBm for a CBER of <1e-6
Modulation Format QPSK in accordance with DVB-S (ETSI EN 300 421)
Modulated Baud Rate 1 MBaud min, 60 MBaud max
Viterbi Values Supported DVB–S: 1/2, 2/3, 3/4, 5/6, 6/7, 7/8
DVB-S2: 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 8/9, 9/10
FEC modes Viterbi and Reed-solomon in accordance with DVB-S.
LDPC (low density parity check) and BCH in accordance with DVB-S2.
Short and Normal FEC blocks in accordance with DVB-S2.
Roll Off 0.2, 0.25, 0.35
Connector Style F-style
Input Termination Impedance 75 Ωnominal
Input Return Loss > 6 dB min, 950 MHz to 2150 MHz typical
LNB Supply Voltage Selectable; 13.0 V ± 1.5 V or 18.0 V ± 1.5 V, with 100 Ω, 5 watt resistor load
LNB Supply Maximum Current 200 mA maximum
LNB 22 kHz Signaling Frequency 17.6 kHz min, 26.4 kHz max (22 kHz ± 20%)
LNB 22 kHz Signaling Amplitude 800 mV p-p with 100 Ωload
LNB Mode DiSEqC 2 (Digital Satellite Equipment Control)
Table 17: DVB-S2 measurements
Characteristic Description
RF Lock RF lock is indicated by LED and Status.
8 MTM400A, IPM400A, and RFM300 Specifications and Performance Verification