The Nokia 1100, and the closely-related variant the Nokia 1101, is a durable and very simple GSM mobile phone produced by Nokia with a 96 x 65 monochrome screen. It is targeted towards developing countries and users who do not require advanced features beyond making calls and SMS text messages, alarm clock, reminders, etc.
The 1100 is similar to the now discontinued 5110/3210/3310 models that were among the most popular cell phones in the world a few years ago before handsets developed several new features such as cameras, polyphonic ringtones and colour screens.
Over 200 million Nokia 1100 cellphones have been sold since its launch in late 2003, making it the world's best selling phone handset, as well as the best selling consumer electronics device in the world, beating Sony's PlayStation 2 (138 million), Apple's iPod (220 million) and Motorola's RAZR (120 million).
Nokia's one billionth phone sold was a Nokia 1100 purchased in Nigeria.
As of early 2009, it has been in the news due to a firmware flaw  in a batch of phones that were manufactured in a plant in Bochum, Germany. The phone can be programmed to receive messages directed to a different phone number, thus receiving sensitive bank or other data. This flaw was brought to authorities' attention after some phones were sold for over US$32,000 . There is only one source, Ultrascan, that all these articles fall back to.
- The 1100 features a built-in flashlight - activated by pressing and holding the "c" key once, or by pressing it twice to lock it on when the keypad is unlocked. It can also be accessed via a menu item.
- The 1100 and 1101 are only able to play monophonic ringtones, which can be selected from the list of 36 pre-installed ring tones or from the 7 self-composed ones.
- It features Nokia's traditional-style navigational keypad, which uses a single button to connect and end calls, bi-directional keys and vibrating alert.
- The Cingular branded version features a built-in AOL Instant Messenger client.
- The 1100 is compatible with the Nokia Xpress-On covers (including matching battery compartments). In addition to the default light blue, orange or black, there are also a dark blue, yellow, red, green and pink offered by Nokia, as well as many 3rd party covers.
- It has been specifically designed for developing countries: its keypad and front face have been designed to be as dustproof as possible, and its sides are non-slip for humid weather.
- Other features include a 50-message capacity (inbox and drafts, with 25 messages in the sent items folder), alarm, stopwatch, calculator, 6 profiles, contacts storage (capacity 50, with the ability to assign different tones and icons to different contacts), and games (Snake II and Space Impact+).
There are five distinct variations within the series: the 1100a, 1100b, 1100i, 1101, and the 1108. They differ as follows:
- The 1100a operates on the GSM-900/1800 network.
- The 1100b operates on the GSM-850/1900 network
- The 1100i adds a built-in Nokia prepaid tracker
- The 1101 replaces the green backlighting with a white backlighting and adds a simple WAP 1.1 browser
- The 1108 also replaces the green backlighting with a white backlighting.
The phone uses a GSM method of activation via SIM card. The Nokia BL-5C battery has a long standby and talk time - this battery is used in more advanced models that have increased power needs for their features, but in the basic 1100 it consumes a fraction of the power and therefore lasts for up to 400 hours between charges. The 1100 is offered for use with a wide range of mobile phone networks. The 1101 has support for Wireless Application Protocol (WAP).
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