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i have a GSM breakout board and a 4g dongle. I'm curious whether it is possible to share one SIM card between both of them? Does anyone know if there is any IC available to do this?

edit: Only one device would use the sim at a time. Ex. first the gsm module for 30 min then the 4g for 1 hour.

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    \$\begingroup\$ Possible duplicate of Ways of Switching between Two Sim Cards \$\endgroup\$
    – uint128_t
    Commented Feb 27, 2017 at 15:49
  • \$\begingroup\$ This is not a duplicate as that links to using 2 SIM cards and 1 interface, here he's doing the opposite, which would require a simple 4 switch...and I don't see why this has been closed? It's a valid question and is not asking for "specific products". \$\endgroup\$
    – not2qubit
    Commented Mar 16, 2017 at 11:03
  • \$\begingroup\$ Use a multiplexer like this: FSA2567 \$\endgroup\$
    – Abdella
    Commented Jul 3, 2021 at 17:14

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It's not possible to share one SIM between two devices.

Well, not easily, anyway. The SIM contains a microcontroller and there is quite a complex communication protocol between it and the device it's installed in that would be confused by connecting two devices to the same SIM. That's in addition to the fact that the two devices would often be trying to drive the same SIM input pins to opposing states at the same time.

You would need to implement an intelligent device that would provide two SIM interfaces, one to each device, and a third interface to the SIM itself, and maintain a separate channel of communication for each interface.

Some service providers allow two SIMs to share the same plan, which is about as close as you're going to get without a great deal of work.

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  • \$\begingroup\$ sorry i wasn't specific enough in my post. Only one device would use the sim at a time. Ex. first the gsm module for 30 min then the 4g for 1 hour. \$\endgroup\$
    – Darellon
    Commented Feb 27, 2017 at 19:01

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