Ericsson T28 – the thinnest phone of 1999

Ericsson T28 – The Thinnest Phone of 1999

The Ericsson T28 was unveiled in 1999 and stunned the entire world with its incredibly slim profile: just 15 mm when closed — an absolute record for the time that no other manufacturer managed to match for years. Its elegant lines, innovative lithium polymer battery and flip mechanism made it immediately an object of desire for millions of European users. To this day it remains one of the most sought-after vintage Ericsson phones among collectors.

History and Context

The Ericsson T28 arrived at a crucial moment in the European mobile phone market. In 1999 Nokia dominated with its robust and practical models, Motorola had just launched the StarTAC, and Siemens was conquering the business market. Ericsson decided to bet everything on design and elegance — a bold decision that paid off immediately. The T28 became the preferred phone of those who wanted to stand out from the crowd, a style symbol even before being a phone.

There are two main variants: the T28 (base version) and the T28s (version with more memory and some additional features). Both share the same essential hardware and the same secret codes.

Design and Materials

High-quality polycarbonate body, backlit keyboard and fold-open flip that protected the keypad when the phone was closed. Open it measured 147 mm, closed just 95 mm. The weight was only 83 grams — extraordinary for the era given the size and features offered. The flip mechanism was designed to last, although after years of use the hinge tends to weaken — see the common issues section.

Complete Technical Specifications

Feature    Detail
Launch year    1999
Network    GSM 900/1800 MHz (Dual Band)
Display    4-level greyscale LCD — 101 x 33 pixels
Battery    Li-Pol (lithium polymer) 500 mAh — very thin
Weight    83 grams
Dimensions open    147 mm
Dimensions closed    95 x 50 x 15 mm
Contact memory    200 contacts
Connectivity    Infrared IrDA
Features    Calendar, calculator, alarm, polyphonic ringtones
WAP    Only on some operator versions
SIM    Mini-SIM (2FF)
Variants    T28 / T28s (extended memory)

The T28's Li-Pol battery was one of the first ever used in a commercial mobile phone — thinner, lighter and safer than the previous NiMH batteries. This technology is now standard on all mobile devices.

Ericsson T28 Secret Codes — Verified

The Ericsson secret code system uses a specific sequence to access the service menu. All codes listed here are verified against primary sources.

Main service menu:
>*<<*<* (right key, asterisk, left key, left key, asterisk, left key, asterisk)
This code opens the hidden Ericsson service menu. The < and > symbols correspond to the left and right arrow keys on the phone.

*#06# → Display IMEI number

Universal GSM codes (work on all Ericsson GSM models):
**04*[old PIN]*[new PIN]*[new PIN]# → Change PIN
**042*[old PIN2]*[new PIN2]*[new PIN2]# → Change PIN2
**05*[PUK]*[new PIN]*[new PIN]# → Unlock SIM with PUK code
*43# / #43# / *#43# → Call waiting ON / OFF / Status
*21*[number]# / #21# / *#21# → Unconditional call forwarding ON / OFF / Status
*61*[number]# → Forward if no answer
*62*[number]# → Forward if unreachable
*67*[number]# → Forward if busy
##002# → Deactivate all forwarding
##004# → Deactivate all conditional forwarding

Ericsson T28 Network Unlock:
The T28 was often locked to European operators of the time. Unlocking requires an NCK code calculated from the IMEI — there is no universal code. The code is entered when the phone displays "Insert correct SIM" or "SIM locked".

Common Issues and Solutions

Battery not holding charge
The original Li-Pol batteries of the T28 after 25 years are almost all depleted — their natural lifespan is 300-500 charge cycles. Modern compatible batteries exist that match the original dimensions. Before buying a used T28, always check the battery condition.

Broken flip or weak hinge
The flip hinge is the most vulnerable point of the T28. After years of opening and closing it tends to loosen or break. In some cases repair with epoxy glue is possible, but complete flip replacement is the most durable solution. Specific T28 spare parts are still available online.

Keys not responding
The most common problem with used T28 units is loss of contact in the keyboard keys. The solution is to clean the contacts under the keys with 99% isopropyl alcohol and a fine brush. In many cases this completely resolves the problem.

Faded display or missing pixels
The LCD display of the T28 can degrade over time, especially if the phone has been exposed to heat or moisture. There is no simple solution — the display must be replaced with a spare.

No network / no signal
If the T28 cannot find a GSM network, first check that the SIM is correctly inserted and that it supports GSM 900/1800 MHz. Some modern SIM cards are only 3G/4G and are not compatible with vintage GSM phones.

Collector Value 2026

The Ericsson T28 is a rare and sought-after phone. Prices vary significantly depending on condition:

Condition    Indicative value
Broken or for parts    €10-25
Working with issues    €30-60
Good condition with working battery    €80-150
Very good condition with intact flip    €120-200
Mint with original box and accessories    €200-350

The T28s (version with more memory) is worth approximately 15-20% more than the base T28 in the same condition. Models with original box, manual and complete accessories are the most sought after.

How to verify authenticity before buying:
Check that the IMEI number on the phone matches the one on the label under the battery. Use *#06# to display the IMEI on screen. Check that the flip opens and closes without play or creaking. Test every key on the keyboard. Check that the display is uniform without missing pixels.

Trivia and Records

The T28 was the first phone in the world to use a lithium polymer battery (Li-Pol) in commercial mass production — a technology that is now universal. It was also one of the first GSM dual-band 900/1800 phones available in Europe. Its design influenced all flip phones of the 2000s. Ericsson used it as a symbol of its "design first" approach that would continue with the T39, T68 models and then Sony Ericsson.

👉 See available Ericsson T28 models at Infosate