IoT Bytes

Bits and Bytes of IoT

Do Analog Dial-Up Modems Still Have Some Relevance in the 4G / 5G World?

Pradeep Singh | 10th July 2018


For some of you, Dial-Up modems may sound like a stone-age technology, but interestingly there are still some unique use-cases where these old devices may play a role for your IoT projects. In this article, I am going to touch some of such use-cases, but before we begin, let’s refresh some fundamentals.

What is a Dial-Up Modem?

“Modem” is an acronym for MOdulator/DEModulator. It converts the digital signal from your computer into an analog signal that can be carried by the phone line, and vice versa. For dial-up modems, due to the technology used to deliver normal phone service (POTS – Plain old telephone service), the fastest download speed available is 56 kilobits (one thousand bits) per second. As per V.34, the data upload speed is limited to 33.6 Kbps (maximum).

Dial-Up Modems and IoT:

Now let’s explore some use-cases where Dial-up Modem can still play a role for your IoT projects –

1. Machine to Machine Communication (M2M):

You could use two modems and create a secure and dedicated connection between two IoT devices using the normal phone lines. If required, one out of these two devices can act as an IoT gateway and further relay the information over other communication channels like the internet.


2. An Internet-Connected Answering Machine for Your Smart Home:

Nowadays most of the Landline Phones have answering machines, but to access your voice-mails or to check the missed calls you need to be physically present near your phone. What if, you are on holiday and want to access these details remotely?

Using the Modem AT commands it’s very easy to collect the Caller ID information or recording a voice-mail as a wave file from the incoming calls. You could save this information in a Database and expose the details using an application (Web App) hosted on the public cloud.

3. IoT Sensors with Voice Alerts / Notifications:

You could make a smart system that in case of a life threating situation detected by a sensor (for example – fire detected by a smoke detector), could call an emergency response team and play a pre-recorded audio message with your home address.

The same thing can be done with various other sensors, for example – if someone tries to open your door while you are away on holidays, the IoT application could call the police department and play a pre-recorded audio message (wave file).

4. Control Devices Using DTMF Digits:

Using the Dial-up Modems you could detect the DTMF digits and perform some operations on IoT Devices. The modem can be connected to a small single board computer like Raspberry Pi and based on the DTMF digits passed by a remote caller, Raspberry Pi can control the actuators using its GPIO pins.


5. Out-Of-Band Management Connection for Remote IoT Sites:

If you lose the Internet connectivity (or some wireless communication channel) with a remote IoT Sensor base station (for ex – a remote weather station), the only option to troubleshoot the issue is to send someone on-site. However, if you have a phone line available at the remote site, you could dial into the remote computer using a dial-up modem and gain the system terminal access for troubleshooting the issue.


6. More Secured Connection Compared to the Internet:

If you need to transfer small but sensitive data the Modems could prove to be useful. Modems can create on-demand point-to-point connections whenever an IoT device has to transfer the information to a remote IoT Gateway. Connecting only when you need to makes hacking into your IoT network very difficult.


Other Applications Where Dial-Up Modems are Still Being Used:

Following are some of the applications where dial-up modems are still popular –

  • Credit Card Payment Terminal in restaurants, movie theaters, or retail stores
  • Ticketing machines in trains stations, bus stations, and airports
  • Pre-pay gas pumps
  • ATM cash machines
  • Stoplight Timing Control – ability to alter signal timing from headquarters to regulate traffic flows
  • Roadside Digital Signs – ability to change messages from headquarters
  • Grocery Store Freezer and Cooler Call Center – ability to monitor temperatures and status as well as receive alerts automatically
  • Safe company – the ability to check temperature, etc. to verify interior of safe is secure
  • Vending machine inventory and status- determine what needs to be replaced before arriving on site
  • Medical devices transferring test results to a computer at a doctor’s office
  • Cell phone tower maintenance on circuits etc.


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