Technical guide
Reference material on Touch Memory and 1-Wire identification — compatibility, family codes, common questions and how to source these parts properly. Written by people who make them.
DS1990A vs TM1990A vs RW1990: what is the difference?
A plain comparison of the read-only DS1990A, its TM1990A equivalent, the rewritable RW1990 blank and the universal Cyfral/Metakom blanks — what each one is for, whether it can be copied, and which readers accept it.
iButton / 1-Wire family code reference table
The first two hex digits of a 1-Wire ROM identify the device type. This reference table maps the common family codes to their iButton and 1-Wire part numbers, so you can identify any key from its printed ID.
Touch Memory & iButton FAQ
Straight answers to the questions buyers and installers actually ask about iButton, DS1990A, TM keys, rewritable blanks, readers, compatibility, lifetime and ordering.
How to wire a Touch Memory reader (TM+, TM−, LED)
The four wires on a TM reader, what each one does, why the LED circuit is independent of the key circuit, and the mistakes that cause a reader to “not work” when it is actually wired backwards.
1-Wire protocol timing: reset, presence, read and write slots
The actual timing numbers behind a 1-Wire key transaction — reset and presence pulse windows, write-1 and write-0 slots, the read sampling window, plus ROM command codes and electrical limits. Measured values from our PR1990 key IC datasheet.
OEM & ODM options: colours, laser marking, ROM ranges, packaging
Exactly what can be customised on a Touch Memory key and what each option costs you in MOQ and lead time — housing colours, your logo, reserved ID ranges, fob assembly and retail packaging.
Sauna & locker lock: how the card hierarchy actually works
Master, pass, user, service and clear cards — what each one can and cannot do, why the master card deliberately cannot open a door, how to switch between single-card and double-card mode, and what to do when a card is lost.
How to source Touch Memory keys: a buyer’s checklist
What to verify before placing a volume order for iButton or TM keys — chip authenticity, read reliability, packaging, custom ROM ranges, MOQ, lead time and the questions worth asking any supplier.
iButton key not reading? A 10-cause troubleshooting ladder
A key that reads nowhere, reads sometimes, or reads on one door but not another — each pattern has different causes. A test-first ladder covering dirty contacts, wrong blank formats, reversed wiring, ground loops, worn readers and dead keys.
Which blank fits which intercom: Vizit, Cyfral, Metakom, Eltis
A brand-by-brand table matching CIS intercom panels to the right key blank — RW1990 for the Dallas branch, RW2000 for Cyfral and Metakom, TM08v2 when one blank must cover everything, T5577 for RFID panels, and OTP blanks where re-copying is banned.
How Touch Memory key copying works — process and equipment
What actually happens when a TM key is duplicated: reading the 64-bit ROM, choosing the right rewritable blank, the write routine, and verification — plus which copier fits a shop counter, a mixed estate or field batch work.
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