I recently obtained several “removable eSIM cards” from esim.me from a friend in a group chat. In short, these eSIM cards are manufactured in the form of ordinary SIM cards, so they can be directly inserted into any mobile phone that supports physical SIM cards, and profiles can be added to the eSIM cards through the Android app provided by esim.me. Although esim.me differentiates the prices of these eSIM cards based on the number of profiles that each eSIM card can join, when I later searched for blog posts online, some people mentioned that the hardware of these eSIM cards at different price points is exactly the same, and esim.me only imposed software restrictions on cards at different price points through the mobile configuration app. And if these eSIM cards are inserted into LTE modules that support eSIM, profiles can be directly added and deleted through the Windows eSIM management interface. However, the current LTE modules that support eSIM are mainly Quectel’s RM-50xQ series (used price 550 yuan) and Dell’s dw5821e (used price 300 yuan) / dw5829e modules. It’s obviously not cost-effective to purchase these LTE modules just to configure the eSIM card. ...

In many parts of the world, mobile phone numbers are increasingly intertwined with online services and personal identity. This is particularly true in mainland China, where a single user may find themselves managing multiple phone numbers for various applications and platforms. While solutions like telegram-sms and SMS-forwarder have emerged to address the inconvenience of managing multiple physical SIM cards, they come with limitations. These apps, typically installed on smartphones, are often hampered by aggressive background process management common on Android devices, leading to unreliable SMS forwarding. Furthermore, the practice of keeping older devices powered on long-term for this purpose introduces safety concerns, such as battery swelling. Perhaps the most significant limitation is the inability to handle phone calls; these apps only address SMS. This article details a project where the author, using an EC20 cellular module and a blend of software tools like asterisk, to overcame these limitations. The setup allows for SMS messaging through instant messaging applications like Telegram, and makes and receives phone calls over the internet using SIP clients, providing a more robust and flexible solution. ...

Graduation Trip Under the ‘Dynamic Zero-COVID Policy’ - Qinghai-Gansu Grand Tour The initial idea for my graduation trip came about at the end of 2021. Back then, the plan was to visit Shanghai and the surrounding areas of Zhejiang. However, with the lockdown in Shanghai and the tightening of restrictions in various regions, by April-May 2022, most cities were requiring individuals to quarantine in place if there was even a single confirmed COVID-19 case in their district. We once thought our graduation trip might be ruined. However, with the “Nine Prohibitions” policy introduced by the State Council in June (specifically, the two prohibitions that impacted our trip were: “Do not arbitrarily expand the scope of travel restrictions from medium- and high-risk areas to other areas” and “Do not impose mandatory dissuasion, isolation, or other restrictive measures on people from low-risk areas”), entry policies in various regions were relaxed. So, we gradually finalized our plan to travel to Tibet in early June. However, with the emergence of new cases in Shenzhen around June 18th, to avoid unnecessary trouble, we ultimately opted to travel to Qinghai and Gansu, where the control policies were relatively loose at the time. With the release of the Ninth Edition of the Diagnosis and Treatment Protocol, which explicitly stated that “isolation of individuals entering from low-risk areas is not allowed,” we finally confirmed our graduation trip plan - a chartered car tour along the Qinghai-Gansu circuit. ...

In order to activate cross-border roaming service for my classmate’s phone, I recently took the time to visit Ma Tso Lung again (the last time was two years ago). Due to the impact of the border closure, compared to August 2019, the number of people going to Ma Tso Lung has significantly increased. The way to get to Ma Tso Lung was slightly different from the last time. This time, I took the 51B minibus from Sheung Shui, which took only about half an hour compared to the two-hour walk in 2019. ...