# US 9,752,792 B2 · Building ventilation system connection detection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,752,792 B2 - Document ID: US9752792B2 - Status: Granted - Kind: B2 - Application number: 14/220,498 - Filed: 2014-03-20 - Published: 2014-09-25 - Granted: 2017-09-05 - Earliest claimed: 2013-03-22 - Assignees: Windowmaster A/S - Applicants: Vkr Holding A/S - Inventors: Jesper Darum - Web page: https://patentgrep.com/patent/US9752792B2 ## CPC - F24F 11/30: for purposes related to the operation of the system, e.g. for safety or monitoring - F24F 11/0001: {for ventilation (F24F11/30 takes precedence)} - F24F 11/88: Electrical aspects, e.g. circuits - F24F 11/89: Arrangement or mounting of control or safety devices - F24F 11/32: Responding to malfunctions or emergencies - F24F 11/33: to fire, excessive heat or smoke - F24F 2007/0025: {using vent ports in a wall} - F24F 2140/40: Damper positions, e.g. open or closed - F24F 2140/50: Load - F24F: AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING (removing dirt or fumes from areas where they are produced B08B15/00; vertical ducts for carrying away waste gases from buildings E04F17/02; tops for chimneys or ventilating shafts, terminals for flues F23L17/02) ## Abstract A building ventilation system (1) comprising a central unit (2) and at least one electrical operating unit (3) for adjusting a movable member of a ventilation device, the central control unit (2) is connected to the at least one electrical operating unit (3) by two power supply wires (4) and configured to provide an operating voltage for operation of the at least one electrical operating unit (3) via the two power supply wires (4), wherein the power supply lines (4) are connected to an end module (5) and the central control unit (2) further is configured to provide a test voltage being lower than the operating voltage, wherein the end module (5) is configured to temporarily vary its load impedance with a predetermined pattern, and the central control unit (2) is configured to detect the temporarily varying load impedance of the end module. ## Claims ### Claim 1 A building ventilation system comprising a central control unit and at least one electrical operating unit for adjusting a movable member of a ventilation device, the central control unit is connected to the at least one electrical operating unit by two power supply wires and configured to provide an operating voltage for operation of the at least one electrical operating unit via the two power supply wires, wherein the two power supply wires are connected to an end module and the central control unit further is configured to provide a test voltage via the power supply wires being lower than the operating voltage, wherein the end module is configured to temporarily vary its load impedance with a predetermined pattern, and wherein the end module is configured to temporarily vary its load impedance by being switchable between a low impedance state and a high impedance state, wherein the end module provides an alternative circuit path circumventing the at least one electrical operating unit when the end module is in the low impedance state, when the test voltage is provided, the end module is in high impedance state, and the central control unit is configured to detect the temporarily varying load impedance of the end module. ### Claim 2 (depends on 1) A building ventilation system according to claim 1, wherein the impedance of the end module is lower than the impedance of the at least one electrical operating unit, when the end module is in the low impedance state. ### Claim 3 (depends on 1) A building ventilation system according to claim 1, wherein the impedance of the end module is higher than the impedance of the at least one electrical operating unit, when the end module is in the high impedance state. ### Claim 4 (depends on 1) A building ventilation system according to claim 1, wherein the end module is in the low impedance state at least 20% of the time when the test voltage is provided. ### Claim 5 (depends on 1) A building ventilation system according to claim 1, wherein the test voltage is less than 50% of the operating voltage. ### Claim 6 (depends on 1) A building ventilation system according to claim 1, wherein the temporarily varying load impedance of the end module is detected in the central control unit by measuring a voltage variation. ### Claim 7 (depends on 1) A building ventilation system according to claim 1, wherein the end module is connected to the central control unit by no more than the two power supply wires. ### Claim 8 (depends on 1) A building ventilation system according to claim 1, wherein the test voltage is less than 25% of the operating voltage. ### Claim 9 (depends on 1) A building ventilation system according to claim 1, wherein the test voltage is about 15% of the operating voltage. ### Claim 10 (depends on 1) A building ventilation system according to claim 1, wherein the end module is in the low impedance state at least 30% of the time when the test voltage is provided. ### Claim 11 (depends on 1) A building ventilation system according to claim 1, wherein the end module is in the low impedance state at least 50% of the time when the test voltage is provided. ### Claim 12 (depends on 1) A building ventilation system according to claim 1, wherein the two power supply lines connect the end module to the central control unit in parallel with the at least one electrical operating unit.