iTTelecom ITT-SR4781 User manual

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ITT-SR4781
3G/4G Serial Device Server
User Manual
RS232/485 to 3G/4G Converter
Modbus RTU to 3G/4G Modbus TCP
RS232/485 P2P 3G/4G Serial Device Server
CopyRight ©2018 Ittelecom Information Technology Co., Ltd. All right reserved

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Version Information
The History of the revision to this document:
History
Date
Version
Revising content
2014-10-16
Rev.1
Release
2016-02-19
Rev.2
Update
Copyright information
Information in this document is subject to change without notice. It is against the law to copy the
document on any medium except as specifically allowed in the license or nondisclosure
agreement. The purchaser may make one copy of the document for backup purposes. No part
of this manual may be reproduced or transmitted in any form or by any means, electronic or
mechanical, including photocopying, recording, or through information storage and retrieval
systems, for any purpose other than for the purchaser’s personal use, without the express
written permission of ITTELECOM information Technology Co., Ltd.

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Content
1. Summary ......................................................................................................................................... 4
1.1 Normal 3G/4G DTU ........................................................................................................... 5
1.2 Multi-host and Modbus Gateway .................................................................................. 7
1.3 P2P 3G/4G Serial Device Server ................................................................................... 7
2. Features .......................................................................................................................................... 9
3. Technical Parameters .................................................................................................................. 9
4. Function ........................................................................................................................................ 10
4.1 Hardware Instruction ..................................................................................................... 10
4.2 Power Saving Mode ....................................................................................................... 13
4.3 Device Configuration and Usage ................................................................................ 13
4.4 Used as 3G/4G Router ................................................................................................... 13
4.5 P2P usage ......................................................................................................................... 13
4.6 485 Character ................................................................................................................... 13
5. Appendix ....................................................................................................................................... 14
5.1 Power On Process .......................................................................................................... 14
5.2 Model Selection ............................................................................................................... 16
6. After-service ................................................................................................................................. 16

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1. Summary
ITT-SR4781 is 3G/4G network solutions launched by ITTELECOM. The Serial contain 4 :
(support Telecom 3G),(Support Modbus TCP Gateway),(Support Mobile and Unicom
3G/4G), (Support P2P). The function of Modbus TCP and P2P can add to models ITT-
SR4781.
Figure 1 ITT-SR4781 Appearance
ITT-SR4781 has RS232/485 interface, can send the data collected by RS232/485 to the cloud
server. Combined with ITTELECOM P2P technology, the users can collect data anytime and
anywhere without building server, the collecting method can also be a virtual serial port. If be ITT-
SR4781, can convert Modbus TCP protocol to Modbus RTU, the users use Modbus TCP to collect
data of RTU devices on the computer. ITT-SR4781 and ITT-SR4781 are the most functional serial
server separately applied to P2P Modbus Gateway of Telecom and Mobile/Unicom, suitable for
PLC monitoring and field data collection very well.
ITT-SR4781 also has the Ethernet port, can use it to communication in the places with Ethernet,

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users can save the 3G/4G traffic. In addition ITT-SR4781 can be used as 3G/4G router to
achieve Ethernet port converting to 3G/4G.
Applications:
PLC remote monitor
Industrial remote control/sensing/measurement
Public Utilities
Meteorological Data Acquisition
Three-Proofing & Hydrology Monitor
Finance, GPRS, etc.
The following is the application of each sub-model respectively. Please refer to section 5
below for model selection.
1.1Normal 3G/4G DTU
The normal 3G/4G DTU can be as TCP Server connected by other network devices,
since the ITT-SR4781 IP is not fixed when under 3G/4G mode, usually it isn’t as TCP
Server, but mostly as TCP Client to connect an fixed IP (or domain name) Server, and
send its collecting data. The software on Server ask data through polling style. The
RS485/232 of ITT-SR4781 can connect with serial device and PLC needed collected,
sending polling command to PLC, and upload the returned data to server. Shown as
Figure 2.
Figure 2 Normal 3G/4G DTU Mode
In this way the purpose of the ITT-SR4781 IP must be set to the server IP, that is to say the

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user must lease a server with a public network IP. However, for some application users
may not have a public network server, because the user dial-up through the router,
then the router must be set on the "port mapping" and "dynamic domain name" to
send ITT-SR4781 data to the server. "Port mapping" and "dynamic domain name"
have the following problems:
1) Some routers are standard telecom, cannot log in so cannot do some settings.
2) "Port mapping" for the average user may be too specialized, set up trouble.
3) "Dynamic domain name" free program may exist stability, real-time problems.
Of course, for the public network IP server users, ordinary ITT-SR4781 is also very
convenient to use. The following lists the differences between ITT-SR4781.
In this way, the Destination IP of ITT-SR4781 must be set to the server's IP, which
means that the user must rent a server with a public network IP. But for some
applications the user may not have a public server, because the user access Internet
through a router dial-up, at this time user must set “Port Mapping "and" Dynamic
Domain Name "on the router so that can send ITT-SR4781 data to the server. There
are some problems with "port mapping" and " Dynamic Domain Name":
1) Some routers are Telecom standard matched, unable to log in so that some
Settings cannot be done.
2) "Port Mapping" may be too specialized for regular users as setting up with trouble.
3) The free scheme of "Dynamic Domain Name" may have stability and real-time
problems.
Of course, for users with public network IP servers, it is also convenient to use the
normal ITT-SR4781.
Model
Support Mode
ITT-SR4781
CDMA2000, Telecom 3G network. If you use a Telecom 4G card, you
can also communicate, but in 3G mode. 3G speed is enough for data
monitoring. So you don't have to deal with 3G CARDS.

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1.2Multi-host and Modbus Gateway
The model with this function is ITT-SR4781. These two models have the following
two functions:
1) Modbus Gateway can be configured. As long as set the “Device/Advanced
Parameter/Transformation Protocol” to "Modbus TCP to RTU", it is switched to
Modbus Gateway mode. The upper computer can be queried with Modbus TCP,
while PLC can use RTU instructions. The Modbus ITT-SR4781 is storage Modbus
Gateway, and the polling is more real-time.
2) Multiple hosts. When set to Modbus Gateway, multiple host queries can be made, and
ITT-SR4781 will answer separately to realize multi-host query. In the non-Modbus
Gateway mode, for the ITT-SR4781 model, you just check the "multi-host" support in
more advanced options it can also implement the multi-host queries.
ITTELECOM-multi-host technology is a technology developed for multi-host monitoring
a device at the same time. In the ordinary serial device server or DTU, when there is A,
B two monitoring computer, A and B can send data to the device, but data the device
received from the serial port will be sent to theAand B at the same time. In other words,
when A and the device communicate, B will receive unwanted data, which will interfere
B's communication. Many software protocols will not be able to adapt to this situation
and may not work.
The ITTELECOM multi-host technology can can achieve the communication
scheduling between A and B computers. When A communicates with the device, the
response data of the device is only sent to A; When B needs to communicate, you can
quickly switch to B. ITT-SR4781 will enable multiple computers to monitor the same
device simultaneously.
1.3P2P 3G/4G Serial Device Server
The model with this function is ITT-SR4781. This model integrates

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ITT-SR4781's P2P technology, which can solve the inconvenience of "Port
Mapping" and "Dynamic Domain Name" in general 3G/4G DTU.
Figure 3 3G/4G DTU Mode of P2P
As shown in FIG. 3, compared with FIG. 2, (a) we increase the ITTELECOM P2P server,
(b) the user computer replaces the monitoring server. Instead of using the server for
monitoring, users can monitor their laptops whenever and wherever they are.
At the beginning of the communication, the P2P software on the user's computer---
Vircom, communicated with the ITTELECOM P2P server. At the same time, ITT-
SR4781 can also communicate with ITTELECOM P2P server, which can establish
direct communication between ITT-SR4781 and Vircom (without the P2P server
forwarding) after the negotiation is done. The software on the user's computer can
communicate via a virtual serial port provided by Vircom or a TCP mock port.
When used, the user only needs to enter the serial number of ITT-SR4781 that needs
to be monitored in Vircom software to establish the P2P connection. The P2P
approach allows users to get rid of the "Port Mapping", "Dynamic Domain Name" and
the server of a public network IP, which can easily and conveniently do monitoring
anytime and anywhere.
The combination of P2P technology and 3G/4G wireless technology has implemented
an innovative monitoring method, which has the following characteristics:
1) Easy to use, users only need to add the serial number of ITT-SR4781 so can go to

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operate, no need any professional operation such as Port Mapping.
2) No additional cost, users no need to lease public server.
3) Support virtual serial port, no need to modify client PLC software, like local serial
communication.
4) As no need to transfer through server, but direct P2P communication, shorten data
communication time, improve the communication real-time, reduce the load of
center server.
5) Support communication type of encryption and user name authentication to ensure
the security of communication.
2. Features
1) The supporting 3G/4G network
a) ITT-SR4781: support EVDO/CDMA2000, Telecom 3G network
b) ITT-SR4781: support 5 modes, TD-LTE/ FDD-LTE/ WCDMA/TD-SCDMA/ GSM,
Unicom 4G/3G/2G, Mobile 4G/3G/2G and Telecom 4G network
2) Provide an Ethernet port, can be used as 3G router. Can be used as Ethernet DTU to
save traffic when on the cable network, same as serial port server.
3) Support P2P connection, no need fixed IP and server, convenient to communicate and
connect.
4) Support Modbus Gateway, as Modbus TCP converting to Modbus RTU.
5) Support multiple hosts monitoring, no interference between each other.
6) SIM card installation in drawer type without disassembly.
7) ITT-SR4781 can be controlled in dormancy via serial port to operate in low power.
3. Technical Parameters
Support Model
ITT-SR4781：SYS EVDO/CDMA2000, Telecom 3G/2G network

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ITT-SR4781 ： Support 5 modes, TD-LTE/ FDD-LTE/ WCDMA/ TD-SCDMA/
GSM, Unicom 4G/3G/2G, Mobile 4G/3G/2G and Telecom 4G network
Transmission Rate
3G network speed: uplink 5.76Mbps download 7.2Mbps
4G network speed: uplink 2Mbps download 68Mbps
SIM Card
Voltage: 3V, 1.8V; Size: Big Card（Small card can buy card sets）
Antenna Interface
Optional 50Ω/SMA glue stick antenna or sucker antenna
Serial Port Type
RS-232/RS-485
Serial Port Parameter
Baud Rate: 1200~115200bps; Data bit: 5～9; Stop bit：1～2; Flow Control:
Hardware, Software; Check bit: None, Odd, Even, Mark, Space
Power Supply
Q2.1 outlet, can be customized to power terminal input
Input Voltage
DC9V~24V
Working Current
< 200mA@9V
Operating
Temperature
-40~85℃
Running temperature:
-40~90℃
Storage temp:
0~95% Non - Condensing
Size:
L×W×H=9.4cm×6.5cm×2.5cm
4. Function
4.1Hardware Instruction
The front view of ITT-SR4781 is shown as FIG. 4.

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Figure 4:ITT-SR4781 Front View
Panel Light:
Indicato
r
Green
BLUE
Active
There is data passing serial port
There is data input from serial port
Link
The network function module has
been initialized
Always bright: the TCP connection is established
Blinking: P2P initialization completed
SYS
Always bright: system in startup
Flashing: the system startup finished
Rapidly flashing: 3G in connection
Always bright: 3G connection success

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Figure 5 Interface Diagram 1
1) The front interface of ITT-SR4781 is shown in figure 5:
a) Power input: interface form Q2.1 socket, DC+9V ~ +24VDC, power needs
over 12W. The default adapter is 9V. Can be customized to power terminal
type input.
b) RS485 signal input.
c) RJ45 interface, Ethernet access end. 3G connection no need to connect RJ45.
If the RJ45 has light on some model, the indicator light flashes indicates that
the network port data is active.
2) The back interface of ITT-SR4781 is shown in figure 6:
Figure 6 Interface Diagram 2
a) Antenna: ITT-SR4781 antenna interface using 50Ω/SMA(female), if external
antenna must use the antenna suitable for 3G/4G working band. ITTELECOM
can provide a gel antenna and a suction antenna that can be sucked onto a
metal shell (by default 2M).
b) SIM card installation: ensure that the device isn’t power on when installing the

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SIM card. Use the pen and screwdriver to push out the SIM card slot, and the
SIM metal surface pushes down into the card slot.
c) DB9: RS232 signal input, support flow control. Among them, the 9th pin is
dormant control, and the high level gives ITT-SR4781 dormant state.
4.2Power Saving Mode
3G devices sometimes don't work long hours and have alarm data opened, which can
save traffic and save batteries. Thus the resting function is designed for ITT-SR4781,
as long as the RS232 pin9 connect to high level 5V, it can cut off almost all the power
of the device. Without connecting pin9, or set to 0, the system is power re-supply.
4.3Device Configuration and Usage
Please install Vircom software on your computer, then connect the Ethernet port of
the computer to ITT-SR4781 Ethernet port. The device can be searched by Vircom
after normal operation with power on, and the serial parameters and IP parameters of
the device can be configured after being searched out.
If configured as 3G access network (not the Ethernet port access), please use Vircom
to configure the device's gateway to 192.168.10.1, the IP to 192.168.10.200, DNS
domain name server to 192.168.10.1, and IP can also be obtained dynamically. If
ITT-SR4781 needs to enable P2P, then go to "More Advanced Settings", check
"Enable P2P", and then click ok and modify Settings.
4.4Used as 3G/4G Router
For more configuration of routers, refer to the instructions of ITT-SR4781 3G/4G router.
4.5P2P usage
Please refer to the file for the use of P2P products.
4.6485 Character
ITT-SR4781 meet the RS485 standard, each ITT-SR4781 can be with 32 terminal 485

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devices. The maximum communication distance is 1200 meter, the resistance of 485
terminal is 120 ohms, usually must use terminal resistance when wiring over 300m.
Pay attention to the wiring, 485+ and 485- must be a twisted-pair, in order to reduce
signal interference.
5. Appendix
5.1Power On Process
Here is a list of the changes of the ITT-SR4781 power on process indicator light to
help users analyze the steps of the device to help troubleshoot problems.
Table 1 ITT-SR4781 Power-on Process (Configured as DHCP Mode)
Time(s)
Status
SYS
LINK
0～1
Power on reset
BLUE
OFF
1～18
System in startup
GREEN
OFF
18～42
The system is started and the
network is initialized
GREEN flash,
frequency is 1 second
OFF
42～60
The 4G module initialization
begins
GREEN flash,
frequency is 1 second
GREEN for 1 second,
then off
60～82
4G first dial-up connection
BLUE flash, frequency
is 0.2 seconds/time
82～126
4G ready for a second dialing
GREEN flash,
frequency is 1 second
OFF
126 ～
150
4G the second dialing
BLUE flash, frequency
is 0.2 seconds/time
OFF
150～
4G in connection
BLUE (with faint
GREEN flash)
The BLUE blinks after
P2P connection.
Table 2 ITT-SR4781 Power-on Process
Time(s)
Status
SYS
LINK
0～1
Power on reset
BLUE
OFF

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1～12
System in startup
GREEN
OFF
12～29
The system is started and the
network is initialized
GREEN flash,
frequency is 1 second
OFF
29～31
The network initialization is
completed, 3G module initialization
begins
GREEN flash,
frequency is 1 second
GREEN
31～52
3G is Connecting
BLUE flash, frequency
is 0.2 seconds/time
GREEN
52～73
3G connecting success
BLUE (with faint
GREEN flash)
GREEN
73～87
P2P initialization is completed (this
step only P2P products set to P2P
mode)
BLUE
BLUE flash,
frequency is 1
second
If you use the ITT-SR4781, the user's card is a 3G card, then need to dial twice, the
first time using the 4G mode dial-up if failed it will use 3G dial-up, this time dialing time
will be slower. But using 2G Mobile card will be one time dialing success in ITT-
SR4781.
Table 3 Ethernet Connection (SIM card not installed) Power-on Process
Time(s)
Status
SYS
LINK
0～1
Power on reset
BLUE
OFF
1～3
System in startup
GREEN
OFF
3～6
The network initialization is
completed
GREEN
GREEN
6～15
P2P initialization is completed
(this step only P2Pproducts set to
P2P mode)
GREEN
BLUE flash,
frequency is 1
second
15～29
System initialization is complete,
normal operation.
GREEN flash,
frequency is 1
second
GREEN(BLUE flash
if P2P Mode)
3G dialing. Although there is no
BLUE flash,
GREEN

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SIM card installed, 3G dialing is
done every time, dial for 2
minutes, and then idle for 1
minute. Repeatedly, in dial-up
periods Ethernet data
communication is not affected.
frequency is 0.2
seconds/time
5.2Model Selection
1)Antenna selection:
Can choose glue stick antenna or suction dish antenna, the suction dish antenna is
2M by default, can be customized 3M antenna.
2)Power input:
The default is the plug type Q2.1 socket, which can be customized for wiring
terminal type power input.
After-service and technical support
Web: http://www.ittelecom.co
Email: [email protected]o