Gsm modem at commands

Types Of GSM Modems

A GSM modem is a cellular modem that works with a Global System for Mobile Communications network. It operates by inserting a SIM card and using the AT command set to interface with a computer. GSM modems can be serial or USB and are used to send SMS, and call and connect to the internet. The types differ depending on the form and functionality.

Here are the common types of GSM modems:

• GSM Terminal: This terminal has been integrated into a single housing combined with a telephone keypad and a display. It is very similar to a telephone, and thus, users will find it easy to use. The terminal is mainly used to send and receive SMS through the GSM network.
• GSM Modem: When people refer to a GSM modem, they mostly refer to a device that can send or receive SMS. The modem exchanges an external RS-232 cable connected to a PC or serial link. Working at high voltages, the modem needs to be reduced to 6V, and the interface between the 6V and the 232V at 12V must be converted for 232V.
• GSM Phone with Data Cable: A mobile phone with a data cable can also be used as a modem to send an SMS gateway. Many people use this method because it is easily accessible in most cases. The cable connects the mobile phone and the PC, and the phone is then instructed on what ports to use to send SMS.

Functions and Features

GSM modems have various functions and features. They include:

• AT Commands: AT commands are essential for the GSM modem's operation. With them, one can control the device through a serial interface. These commands help with things like making and receiving calls, sending and receiving messages, and configuring network settings.
• Serial Communication: GSM modems use serial communication to connect with a PC or microcontroller. Most modems use RS-232 or TTL levels for the serial connection. The modem's serial port allows the transmission of data and commands back and forth.
• SMS Messaging: GSM modems support SMS messaging. They are used to send and receive text messages over the GSM network. The SMS functions and commands allow one to send a message, receive, store, and delete messages.
• MMS Messaging: MMS messaging on the GSM modem allows multimedia messages to be sent and received. The multimedia messages can contain images, video clips, audio, and text. MMS commands compose a multimedia message and send it to a recipient's mobile number.
• Voice Communication: The AT commands on the GSM modem can be used to make voice calls. The modem can send a voice call to a specified number or answer an incoming voice call. Some advanced modems also support duplex communication, which allows two parties to talk simultaneously, just like on a phone call.
• Fax Services: Some GSM modems can send and receive faxes over the GSM network. This feature is helpful for businesses that still use fax machines for document transfer. The modem converts the fax into a digital format that can be transmitted via SMS or data call.
• Data Connectivity: Certain GSM modems have the capability to transmit data. This feature is really important for applications that need internet access in places where wired connections are not available, like banks' ATMs or remote weather stations. The modems turn a cellular signal into a Wi-Fi or Ethernet connection so that people can get online easily. To do this, they use something called packet-switched data. Some examples of the types of data-transmitting modems are GPRS, EDGE, CDMA, and HSPA.

Applications of GSM Modem at Commands

Since GSM modems are essential for wide communication systems, they are used in various industries for many applications. Some of the notable applications highlighted below are accompanied by brief descriptions:

• Remote Monitoring: Industries use GSM modems to monitor machines and other equipment. In cases of abnormal conditions, modem communication is used to send alerts via SMS.
• Fixed Cellular Replacement: Landline phones can be replaced with GSM modems, which can also be used to call and send SMS. This is important for businesses and industries operating in remote areas.
• Telematics: The tracking and supervision of vehicles, ships, airplanes, and other mobile equipment can be made possible with the aid of GSM modems. Logistics, transportation, and the military all make significant use of this technology.
• Industrial Automation: GSM Modems are important components in industrial automation systems. They enable industries to remotely control various systems and machinery by sending commands via SMS or from a PC or mobile phone.
• IoT Connectivity: The Internet of Things (IoT) is a system of interrelated physical devices connected to the internet. The GSM modem AT command is important in providing Internet connectivity to IoT devices.
• Alarm and Security Systems: Alarm systems use GSM modems to alert users of possible security breaches. They can notify users through messages or calls when there is unauthorized access or an attempt to breach security.
• Healthcare Applications: Healthcare systems use GSM modems to monitor their patients' conditions. These modems can be embedded within devices to send information and alerts about the patients' states.
• SMS Marketing: Businesses can contact consumers or clients via promotional SMS messages thanks to GSM modems. Marketing and brand awareness can be boosted through bulk messaging.
• Point-of-Sale Transactions: In locations with no fixed-line phone systems, GSM modems can process credit and debit card payments, vital for businesses or merchants operating in remote areas.
• Utilities and Smart Metering: Utility companies can use GSM modems to collect data from meters that measure consumption of water, electricity, and gas. This allows for data transmission and remote monitoring.

How to Choose GSM Modem AT Commands

It is essential to use the proper GSM modem when using AT commands for GSM to avoid device-level variants and commands. The following is a GSM modem purchasing guide.

• Consider Modem Compatibility:

  Enquire about the vendor or service provider's GSM modem and network compatibility. This is because not all modems can offer commands as set in a certain standard. Looking into specifics like the modem's product category and technical specifications can help the purchaser know whether they should use the modem to integrate command execution into their system. The organization or person inquiring should also inspect the modem to ensure correct AT command support standards.

• Method of Connection:

  A purchaser should be aware of how they will integrate the modem into the existing infrastructure, which is by serial RS-232 or USB connection. Knowing this will help users understand the installation method and any required driver and port mapping.

• Modem Command Set:

  The entire set of commands may differ from one GSM modem to another, so look at the documentation that comes with the modem to get an overview of the essential commands needed for operations such as:

  • Basic Communication: Commands for sending and receiving messages.
  • Network Commands: Commands for Network Registration and Signal Quality Check.
  • Call Commands: Commands for Making Calls and Related Actions.
  • Message Commands: Commands for Sending and Receiving SMS.
  • SIM Commands: Commands for SIM Operations such as PIN Check.
  • Power and Reset Commands: AT+CPWR= for Power Down and Resetting the Modem.

• Command Execution:

  To execute the AT commands for GSM, connect the PC to the modem using a serial cable or USB cable, launch a terminal program like PuTTY or HyperTerminal, select the modem's COM port, set the baud rate, and establish communication by sending commands and receiving responses.

Gsm modem at commands Q&A

Q1: What GSM Modem AT Commands are essential for beginners to know?

A1: Beginners should learn basic commands like AT (to check communication), ATE (to enable echo), and AT+CMGF (to set SMS text mode).

Q2: How can I find the right GSM modem to support the desired AT commands?

A2: To find the right GSM modem, one must check the documentation or product specifications to see the supported AT commands.

Q3: Are there tools to help learn or test GSM Modem AT Commands?

A3: Yes, tools like PuTTY, Tera Term, or CoolTerm can help to learn and test the commands by providing a terminal interface to communicate with the modem.

Q4: How should one start executing GSM Modem AT Commands?

A4: To start executing the commands, one should establish a connection with the modem through a serial port or over TCP, using a terminal application to type commands and see responses from the modem.

Q5: Where can one find documentation or help with the AT Commands for a specific modem?

A5: To find help, one can look at the manufacturer's website, as they usually have manuals or command guides for their modems. Online forums and documentation can also be of help.