---
title: "Dual SIM (DSSS): What does “Dual SIM” mean—and why can only one SIM be online at a time?"
slug: "dual-sim-dsss-what-does-dual-sim-mean-and-why-can-only-one-sim-be-online-one-tim"
updated: 2026-05-28T13:07:14Z
published: 2026-05-28T13:07:14Z
canonical: "docs.insys-icom.com/dual-sim-dsss-what-does-dual-sim-mean-and-why-can-only-one-sim-be-online-one-tim"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.insys-icom.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Dual SIM (DSSS): What does “Dual SIM” mean—and why can only one SIM be online at a time?

With **Dual SIM Single Standby (DSSS)**, the device contains two SIM cards, but only **one SIM** is active at a time. The second SIM remains on standby and is used when a switch is necessary. The added value, therefore, lies not in parallel operation, but in robust and easily manageable redundancy.

If the primary network fails or no longer meets defined requirements, you can switch to the second SIM. This allows you to increase the availability of the mobile connection without unnecessarily complicating the architecture. It is important to note that **DSSS stands for redundancy, not for load balancing or active-active operation**.

## Related

- [Dual-SIM Best Practices: Which SIM combinations make sense?](/dual-sim-best-practices-which-sim-combinations-make-sense.md)