# US 10,644,748 B2 · Network test instrument with cable connection and signature testing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,644,748 B2 - Document ID: US10644748B2 - Status: Granted - Kind: B2 - Application number: 14/836,770 - Filed: 2015-08-26 - Published: 2017-03-02 - Granted: 2020-05-05 - Earliest claimed: 2015-08-26 - Assignees: Viavi Solutions Inc. - Applicants: Viavi Solutions Inc. - Inventors: Robert J. Flask - Web page: https://patentgrep.com/patent/US10644748B2 ## CPC - H04B 3/46: Monitoring; Testing - G01R 31/11: using pulse reflection methods - H04Q 5/00: Selecting arrangements wherein two or more subscriber stations are connected by the same line to the exchange - H04Q 2213/1301: Optical transmission, optical switches - H04Q 2213/13012: Hybrid fiber coax, HFC - H04Q 2213/1316: Service observation, testing - H04B: TRANSMISSION - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H04Q: SELECTING (switches, relays, selectors H01H; wireless communication networks H04W) ## Abstract A test instrument can be coupled to a test point and measure signals in the network. The test instrument may determine whether the test instrument is connected to a cable of the network and provide notification if the test instrument is not connected to a cable. The test instrument may also detect when it is connected to a customer premises that has been previously been tested through reflected signal signatures. ## Claims ### Claim 1 A test instrument comprising: at least one port connectable to a cable; a pulse generator to output a reflectometry pulse to the at least one port; a measurement circuit to measure characteristics of a reflected pulse received on the at least one port; a data storage storing a signature of a reflected reflectometry pulse for a predetermined test location, wherein the signature is a unique signature associated with the predetermined test location; and a processing circuit to: determine whether the at least one port of the test instrument is connected to a minimum length cable based on the measured characteristics, determine, in response to determining the at least one port of the test instrument is connected to the minimum length cable, channel diagnostic information for signals received via the at least one port, wherein the channel diagnostic information comprises at least one of a signal level of a detected downstream channel, a modulation type of the detected downstream channel, signal-to-noise (SNR) for the channel, bit error ratio (BER) for a detected channel, modulation error ratio (MER) for the detected channel, ingress under a carrier, in Channel Frequency Response (ICFR), adaptive equalization coefficients, Digital Quality Index (DQI), and use a signature comparison technique to determine whether a signature determined from the measured characteristics of the reflected pulse matches the stored signature to determine whether the test instrument is connected at the predetermined test location, wherein a match between the signature determined from the measured characteristics and the stored signature that is unique to the predetermined location indicates that the test instrument is connected at the predetermined test location associated with the stored signature. ### Claim 2 (depends on 1) The test instrument of claim 1, wherein, in response to determining the at least one port is not connected to the minimum length cable, the processing circuit performing at least one of providing notification that the test instrument is not connected to the minimum length cable and preventing measurements of the signals received via the at least one port. ### Claim 3 (depends on 1) The test instrument of claim 1, wherein to determine whether the at least one port of the test instrument is connected to the minimum length cable, the processing circuit is to determine a reflection time of the reflectometry pulse, and determine whether the minimum length cable is connected to the at least one port based on the reflection time. ### Claim 4 (depends on 3) The test instrument of claim 3, wherein the processing circuit determines whether the minimum length cable is connected to the at least one port based on the reflection time and a signal transmission velocity of the cable. ### Claim 5 (depends on 1) The test instrument of claim 1, wherein the reflectometry pulse comprises a time domain reflectometry pulse or a frequency domain reflectometry pulse. ### Claim 6 (depends on 1) The test instrument of claim 1, wherein the measured characteristics comprises reflection time and amplitude of the reflected pulse. ### Claim 7 (depends on 1) The test instrument of claim 1, wherein the reflected pulse comprises the reflectometry pulse reflected from an impedance back towards the at least one port. ### Claim 8 (depends on 1) The test instrument of claim 1, wherein the signature is based on amplitude and time of at least one peak in the reflected pulse. ### Claim 9 A test instrument method comprising: transmitting a reflectometry pulse from a port of the test instrument; receiving a reflected pulse on the port in response to transmitting the reflectometry pulse from the port; measuring characteristics of the reflected pulse received via the port, wherein the reflected pulse is the reflectometry pulse reflected from an impedance in a system connected to the port; storing a signature of a reflected reflectometry pulse for a predetermined test location wherein the signature is a unique signature associated with the predetermined test location; determining, by a processing circuit, whether the port is connected to a minimum length cable based on the measured characteristics; determining, in response to determining the at least one port of the test instrument is connected to the minimum length cable, channel diagnostic information for signals received via the port, wherein the channel diagnostic information comprises at least one of a signal level of a detected downstream channel, a modulation type of the detected downstream channel, signal-to-noise (SNR) for the channel, bit error ratio (BER) for a detected channel, modulation error ratio (MER) for the detected channel, ingress under a carrier, in Channel Frequency Response (ICFR), adaptive equalization coefficients, Digital Quality Index (DQI); using a signature comparison technique to determine whether a signature determined from the measured characteristics of the reflected pulse matches the stored signature to determine whether the test instrument is connected at the predetermined test location, wherein a match between the signature determined from the measured characteristics and the stored signature that is unique to the predetermined location indicates that the test instrument is connected at the predetermined test location associated with the stored signature; and performing, in response to determining the port is not connected to the minimum length cable, at least one of providing notification that the test instrument is not connected to the minimum length cable and preventing measurements of signals received via the port. ### Claim 10 (depends on 9) The test instrument method of claim 9, wherein determining whether the port is connected to the minimum length cable comprises: determining a reflection time of the reflectometry pulse; and determining whether the minimum length cable is connected to the port based on the reflection time. ### Claim 11 (depends on 10) The test instrument method of claim 10, wherein determining whether the minimum length cable is connected to port is based on the reflection time and a signal transmission velocity of a predetermined cable. ### Claim 12 (depends on 9) The test instrument method of claim 9, wherein the reflectometry pulse comprises a time domain reflectometry pulse or a frequency domain reflectometry pulse. ### Claim 13 (depends on 9) The test instrument method of claim 9, comprising: providing notification that the test instrument is not connected at the predetermined location in response to determining the signatures do not match; and allowing measurement of the signals at the test instrument in response to determining the signatures match. ### Claim 14 (depends on 9) The test instrument method of claim 9, wherein the signature of the reflected pulse is based on amplitude and time of at least one peak in the reflected pulse.