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Understanding the SIM: Crash Course

Understanding the SIM: Crash Course

SIM cards were introduced as a means to port connectivity securely, enabling a user to keep control of their subscription while changing devices. SIM form factors have progressed over the years becoming smaller as technology improvements are made.

It started off with 1FF, the “Full-size” SIM, introduced in 1991. The size of a standard credit card we carry today, these SIMs would be too large to be used in mobile phones today.

The “normal” SIMs


Different SIM form factors

Then came the commonly recognizable form factor – the 2FF “Mini” SIM which was used since 1996 in mobile phones, until we saw rapid reduction in sizes in recent times with 3FF and 4FF SIMs, commonly referred to as Micro SIM and Nano SIM.

At ConnectedYou, we have combined all the Form-Factors (2FF, 3FF and 4FF) into one SIM – the 3 in 1 SIM allowing you to use the SIM in more number of devices without having the user “cut” the SIMs themselves.

Industrial SIMs

With the increase of Machine-to-Machine (M2M) applications, there came a need to make SIMs more environmentally robust. While normal SIMs are operational within a temperature range of -25°C and +85°C, industrial grade SIMs are produced with higher resistance with an expanded temperature range of -40°C and +105°C. Other factors such as corrosion and impact on SIMs from vibrations were also improved.

Industrial SIMs for IoT & M2M deployments

In M2M use cases, it was seen that SIMs were expected to remain within machines for a long period of time and were often difficult to get access to. While consumers could easily swap SIM cards, it was much more difficult for such swaps in machines. This gave birth to requirements for SIMs to have a longer operational life – not just in hardware but also in software. Industrial SIMs generally also have a longer life-span (around 10-15 years), higher number of read/write cycles to ensure SIMs don’t “die” too quickly and are in harmony with a device’s lifecycle.

Embedded SIMs (eSIMs)

With M2M becoming mainstream and buzz words such as Internet of Things (IoT) becoming popular, requirements on SIM technology robustness increased further. Environmental factors such as humidity, vibration-tolerance, acceleration shocks, etc. had become more demanding in their tolerance level needs. Moving parts tend to have lower resistance in electronics, and so came the solution of embedding SIMs. This gave birth to the Machine Form Factor with the widely accepted Surface Mounted Device (SMD) form factor now being MFF2.

IoT use cases enabled by eSIMs

The MFF2 comes with a minimum of industrial grade quality, and is further enhanced for the automotive sector. Purpose built to comply with the automotive sectors’ tough quality management standards (such as PPAP, AEC-Q100) and with higher data retention span (15-17 years) the automotive eSIM is the top of the range eSIM.

While the MFF2 benefits with a superior quality, there is a downside of being non-removable. Since the MFF2 SIMs are soldered onto the circuit boards, replacing them are not easy. That does provide an upside too – the added benefit of physical security, as it’s not easy to tamper with or steal a soldered eSIM.

eUICCs and Subscription Management

There was now a need to replicate a secure “SIM swap” on a software level on the eSIMs. This gave birth to a new software mechanism for eSIMs. On the SIM it is commonly referred to as an eUICC operating system (OS). On the server side (for management of eUICCs) it is referred to as Subscription Management Platform or Remote SIM Provisioning Platform.

While previously, a SIM would belong to a particular network operator, the eUICC allows the user to take control of the connectivity. The owner of the SIM is allowed to select and swap network operators securely by downloading credentials from the “Subscription Management” platform. Thus using an eUICC-eSIM or eUICC plug-in SIM rather than the standard eSIM/ plug-in SIM opens up the option for the user to change their network operator in the future without touching the hardware.

So why aren’t all SIMs programmed as eUICCs?

From technical to political & regulatory challenges, there are several reasons that network operators don’t enable this.

Technically, enabling eUICCs requires every Network Operator to integrate their Subscription Management platform into all other Network operators – which is easier said than done! There are so many Network operators out there, and the integrations are a resource intensive task – the ROI just doesn’t make the effort feasible.

Difference between SIM & eSIM

Politically, some network operators may not be too keen to enable an exit option, as they fear churn and loss of subscribers. Especially in IoT, where a loss of a “customer” could equate to loss of large volumes of devices from their network, easily reaching millions.

Regulatory requirements like mandatory user registrations or Know Your Customer make the enablement from being more than just about the eUICC technology. New processes need to be introduced, new software mechanisms created to cater such requirements “remotely”. After all what’s the point of enabling a technology eradicating the need for physical intervention, while still having processes that require you to be physically present?

How does ConnectedYou make a difference?

ConnectedYou (CY) offers the CY SIM that is decoupled from the connectivity providers – a SIM powered by eUICC technology offered in both plug-in (3in1) and embedded format. From the CY connectivity hub, users can select the Network operators they prefer based on factors that can define these decisions such as price, geography, network strength, etc.

The CY connectivity hub is an orchestration layer from where we make integrations into different Network operators. Since the Network operators only need to make an integration with us, their effort is better justified. Even more so, considering they integrate to gain customers via our ecosystem – it improves their customer acquisition cost as they don’t bear the hardware costs of SIMs and gain customers organically from the integration.

The same technology that is feared by network operators to be a catalyst for churn is now an enabler for new business and a catalyst for IoT growth. Network operators can focus on improving their services rather than spend resources on needless integrations into other network operators.


Typically, the price of the products are directly proportional to their benefits and deciding a SIM/network operator & SIM form factor for an IoT/ M2M project is more about understanding the use case.

Some questions to ask: Are there particular environmental factors to consider? Is the longevity of the product important? Do you have easy access to the device? Can you trust your connectivity provider for the life-span of the product? Do the benefits of the embedded form factors outweigh the costs? The process of getting a eSIM soldered is also vastly different from plugging in a SIM into a slot, so this requires consideration as well.


If you are finding it difficult to make a decision, feel free to reach out to us – we are always happy to help. We orchestrate the critical components that include - eUICC enabled SIMs/ eSIMsglobal IoT/ M2M connectivity, unified monitoring & management, and remote SIM provisioning capabilities into a single solution as a one-stop-shop. Here’s why our product is the best solution for your enterprise - 

  • The largest network of 2G, 3G4G, 5GLTE-M and NB-IoT networks 
  • Connectivity for countries with permanent roaming restrictions
  • Transparent Pay-As-You-Go pricing without hidden charges or minimum commitments
  • Single contract enabling hassle free multi-supplier sourcing without lock-ins with any connectivity provider
  • Unified platform to manage your IoT/ M2M SIM cards irrespective of the connectivity supplier
  • Capability to switch connectivity suppliers remotely without SIM replacement and  without any additional transaction costs
  • Central support desk for all connectivity issues

Written by - Arun Shankar

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