# US 6,212,402 B1 · System connector > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,212,402 B1 - Document ID: US6212402B1 - Status: Granted - Kind: B1 - Application number: 08/746,339 - Filed: 1996-11-08 - Granted: 2001-04-03 - Earliest claimed: 1996-11-04 - Assignees: Telefonaktiebolaget LM Ericsson - Inventors: Jan Ragnar Rubbmark; Göran Claes Pehrsson; Magnus Hans Hansson - Web page: https://patentgrep.com/patent/US6212402B1 ## CPC - H03K 19/01843: {with a bidirectional operation} - H03K 19/01806: {Interface arrangements} - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) ## Abstract A system connector is provided to allow for the communication of digital signals between two devices functioning at different operating voltages. The connector allows for the interfacing of the high and low signal logic levels through the use of each devices own operating voltage without the need for complex signal conversion of voltage levels. The connector may be used to allow communication between mobile phones and their accessories. The system connector may be incorporated into an accessory or portable device allowing the signal level interfacing between the portable device and accessory. The system connector supplies a high-level or low-level digital signal to a first device operating at a first voltage in response to a corresponding high-level or low-level digital signal from a second device operating at a second voltage. In addition, the system connector may also provide a high-level or low-level digital signal from a second device operating at a second voltage in response to a corresponding high-level or low-level digital signal from the first device operating at the first voltage. ## Claims ### Claim 1 A system for connecting detachable first and second devices, wherein each device functions at a different operating voltage, comprising: an output of the first device for outputting a high-level voltage of the first device; an input of the first device for inputting digital signals; a digital transistor for switching between a high-level voltage and low-level voltage; and an output of the second device for outputting digital signals, wherein the digital transistor provides the high-level voltage of the first device from the first device output to the input of the first device in response to detecting a high-level voltage from the second device output and provides a low-level voltage to the input of the first device in response to detecting a low level voltage from the second device output, wherein a high-level input from the second device to the digital transistor opens the transistor connecting the input of the first device to a ground of the second device, and wherein a low-level input from the second device to the digital transistor closes the transistor connecting the input of the first device to an operating voltage of the first device, and wherein the first device is a mobile phone and the second device is a mobile phone accessory. ### Claim 2 (depends on 1) A system according to claim 1, wherein the high-level voltage of the first device is approximately the operating voltage of the first device and the low-level voltage of the second device is approximately the ground of the second device. ### Claim 3 A system connector providing digital communication between two devices comprising: first means for supplying a high-level or low-level digital signal to a first device having a first operating voltage in response to a corresponding high-level or low-level digital signal from a second device operating at a second voltage; and second means for supplying a high-level or low-level digital signal to the second device operating at the second voltage in response to a corresponding high-level or low-level digital signal from the first device operating at the first voltage, wherein the first means includes a digital transistor and wherein a high-level input from the second device to the digital transistor opens the transistor connecting an input of the first device to a ground of the second device, and wherein a low-level input from the second device to the digital transistor closes the transistor connecting the input of the first device to the operating voltage of the first device. ### Claim 4 (depends on 3) The system of claim 3, wherein the first device is a mobile phone. ### Claim 5 (depends on 4) The system of claim 4, wherein the first and second means are located in the accessory. ### Claim 6 (depends on 3) The system of claim 3, wherein the second device is a mobile phone accessory. ### Claim 7 (depends on 3) The system connector of claim 3, wherein the second means includes means for comparing a reference signal and the high-level or low-level digital signal supplied from the first device, and wherein a comparator outputs a high-level signal according to the operating voltage of the second device when the digital signal is a high-level value according to the operating voltage of the first device and outputs a low-level signal according to the operating voltage of the second device when the digital signal is a low-level value according to the operating voltage of the first device. ### Claim 8 A combination mobile phone and accessory comprising: first means for supplying a high-level or low-level digital signal to a mobile phone in response to a corresponding high-level or low-level digital signal from the accessory; and second means for supplying a high-level or low-level digital signal to the accessory in response to a corresponding high-level or low-level digital signal from the mobile phone, wherein the first means includes a digital transistor and wherein a high-level input from the second device to the digital transistor opens the transistor connecting an input of the first device to a ground of the second device, and wherein a low-level input from the second device to the digital transistor closes the transistor connecting the input of the first device to the operating voltage of the first device. ### Claim 9 (depends on 8) The combination mobile phone and accessory according to claim 8, wherein the mobile phone and accessory have different operating voltages. ### Claim 10 (depends on 9) The combination mobile phone and accessory according to claim 9, wherein the mobile phone has an operating voltage of approximately 5 volts and the accessory has an operating voltage of approximately three volts. ### Claim 11 (depends on 8) The system connector of claim 8, wherein the second means includes means for comparing a reference signal and the high-level or low-level digital signal supplied from the first device, and wherein a comparator outputs a high-level signal according to the operating voltage of the second device when the digital signal is a high-level value according to the operating voltage of the first device and outputs a low-level signal according to the operating voltage of the second device when the digital signal is a low-level value according to the operating voltage of the first device.