These RW1990 chips we use an imported one, which passed reliable performance than others, the CMOS microcircuit is basically a 64-bit single digital code electronic . The code is stored in internal non-volatile memory. Data exchange is performed by the 1-Wire Protocol, which requires a single data pin and the common pin. The microcircuit supports the ROM Search 1-Wire Protocol function, which makes it possible for multiple devices to work on one bus. This Protocol determines the conditions of alteration of the state of the bus and the time intervals during the synchronization by means of the interruptions of synchro-pulses of the control device. The reading and writing of the data are performed by junior thian bit forward. Chip Type: RW1990 1 RW1990 ibutton 2. Water resistant 3. Rewritable, DS1990A and TM1990A iButton, 4. Can be copied, RW1990 Technique parameters: America encryption Failure rate: 1 / 100,000 Memory: 8KB RAM Inductive type: Contact R / W and encrypt R / W times: 1,500,000,000 Operating temperature: -40 ~ 85 Lifespan: more than 20 years Rewritable button RW1990A-F5 Read-write card, compatible with ds1990a. Rewritable, DS1990A and TM1990A iButton, RW1990 64-bit unique record number; Integrated Multidrop controller for 1-wire network; Digital identification by momentary contact TM card, also known as Contact memory, electronic ke3.5y Stainless steel package with su304 #, Resistant, never rust, Corrosion; Heat-resistant; Anti-variant; Strong sealing; For security patrol, sauna door locks, electronic door locks, Door intercom, card systems, identification, banking, Communications, rail transportation, transportation and many fields color: random colors, don't accept the specified color Material: plastic size: 16.25x5.89mm Package Contents: 10 x RFID Contact Memory Key Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.