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  <xs:element id="sncr_NetIncomeLossIncludingPortionAttributableToNoncontrollingInterestAndRedeemableInterests" abstract="false" name="NetIncomeLossIncludingPortionAttributableToNoncontrollingInterestAndRedeemableInterests" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_ServiceLineAxis" abstract="true" name="ServiceLineAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="sncr_MessagingMember" abstract="true" name="MessagingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_CapitalStockSharesAuthorized" abstract="false" name="CapitalStockSharesAuthorized" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="sncr_TemporaryEquityPreferredStockRedemptionValue" abstract="false" name="TemporaryEquityPreferredStockRedemptionValue" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_RevenueRemainingPerformanceObligationExpectedTimingofSatisfactionPercent" abstract="false" name="RevenueRemainingPerformanceObligationExpectedTimingofSatisfactionPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_AssetPurchaseAgreementConsiderationReceived" abstract="false" name="AssetPurchaseAgreementConsiderationReceived" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_DebtInstrumentUnderwritersOptionToPurchase" abstract="false" name="DebtInstrumentUnderwritersOptionToPurchase" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_StockIncentive2000And2006PlanMember" abstract="true" name="StockIncentive2000And2006PlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_DisposalGroupIncludingDiscontinuedOperationContingentConsideration" abstract="false" name="DisposalGroupIncludingDiscontinuedOperationContingentConsideration" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_DebtInstrumentPercentageOfDebtHoldersDemandFullRepaymentOnDebtDefaultAmount" abstract="false" name="DebtInstrumentPercentageOfDebtHoldersDemandFullRepaymentOnDebtDefaultAmount" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_SoftwarePurchasedMember" abstract="true" name="SoftwarePurchasedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_ServiceLineDomain" abstract="true" name="ServiceLineDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_EffectiveIncomeTaxRateReconciliationForeignBasisDifferencesPercent" abstract="false" name="EffectiveIncomeTaxRateReconciliationForeignBasisDifferencesPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_SequentialTechnologyInternationalLLCMember" abstract="true" name="SequentialTechnologyInternationalLLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_ChangesInContractLiabilitiesRollForward" abstract="true" name="ChangesInContractLiabilitiesRollForward" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="sncr_DebtInstrumentAccretionOfInterest" abstract="false" name="DebtInstrumentAccretionOfInterest" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsAdjustmentInPeriodWeightedAverageGrantDateFairValue" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsAdjustmentInPeriodWeightedAverageGrantDateFairValue" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="sncr_TemporaryEquityPaymentOfPreferredDividendShares" abstract="false" name="TemporaryEquityPaymentOfPreferredDividendShares" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="sncr_A2014ConvertibleSeniorNotesDue2019Member" abstract="true" name="A2014ConvertibleSeniorNotesDue2019Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfCompensationPlans" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfCompensationPlans" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncr_DisposalGroupIncludingDiscontinuedOperationRevenueTargetsToBeReceived12MonthsFromClosingDateContingentConsideration" abstract="false" name="DisposalGroupIncludingDiscontinuedOperationRevenueTargetsToBeReceived12MonthsFromClosingDateContingentConsideration" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_EffectiveIncomeTaxRateReconciliationOperatingLossCarryforwardsPercent" abstract="false" name="EffectiveIncomeTaxRateReconciliationOperatingLossCarryforwardsPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_ProfessionalServicesMember" abstract="true" name="ProfessionalServicesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_DurationofCustomerContract" abstract="false" name="DurationofCustomerContract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="sncr_DebtInstrumentFaceAmountInclusiveOfUnderwritersOptionToPurchase" abstract="false" name="DebtInstrumentFaceAmountInclusiveOfUnderwritersOptionToPurchase" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_TopFiveCustomersMember" abstract="true" name="TopFiveCustomersMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_ImpairmentOfLonglivedAssetsAndCapitalizedSoftware" abstract="false" name="ImpairmentOfLonglivedAssetsAndCapitalizedSoftware" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_AccruedThirdPartyTechServices" abstract="false" name="AccruedThirdPartyTechServices" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_ContractWithCustomerLiabilityIncludingNewContractRevenueRecognized" abstract="false" name="ContractWithCustomerLiabilityIncludingNewContractRevenueRecognized" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_TemporaryEquityDividendsValue" abstract="false" name="TemporaryEquityDividendsValue" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_EffectiveIncomeTaxRateReconciliationGlobalIntangibleLowTaxIncomeInclusionPercent" abstract="false" name="EffectiveIncomeTaxRateReconciliationGlobalIntangibleLowTaxIncomeInclusionPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_ContractFulfillmentCostsMember" abstract="true" name="ContractFulfillmentCostsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_DeferredTaxAssetsBasisDifferences" abstract="false" name="DeferredTaxAssetsBasisDifferences" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_DepreciationDepletionandAmortizationNetofImpairment" abstract="false" name="DepreciationDepletionandAmortizationNetofImpairment" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_VestingSecondAnniversaryMember" abstract="false" name="VestingSecondAnniversaryMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_EightPointThreeSevenFivePercent2500ParValueSeniorNotesDue2026Member" abstract="true" name="EightPointThreeSevenFivePercent2500ParValueSeniorNotesDue2026Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_NumberOfVotesEachShare" abstract="false" name="NumberOfVotesEachShare" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncr_DebtInstrumentProceedsFromSaleOfStockTransactionsUsedForRedemptionOfShares" abstract="false" name="DebtInstrumentProceedsFromSaleOfStockTransactionsUsedForRedemptionOfShares" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_DebtInstrumentProceedsFromSalePercentage" abstract="false" name="DebtInstrumentProceedsFromSalePercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_OtherSundryNonoperatingIncomeExpenseNet" abstract="false" name="OtherSundryNonoperatingIncomeExpenseNet" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_PreferredStockDividendRatePercentageOne" abstract="false" name="PreferredStockDividendRatePercentageOne" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseBadDebtAdjustmentPercent" abstract="false" name="EffectiveIncomeTaxRateReconciliationNondeductibleExpenseBadDebtAdjustmentPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_RedeemableNoncontrollingInterestMember" abstract="false" name="RedeemableNoncontrollingInterestMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_TransactionServicesMember" abstract="true" name="TransactionServicesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_FiniteLivedIntangibleAssetsExcludingCapitalizedSoftwareCostsInDevelopmentStageNet" abstract="false" name="FiniteLivedIntangibleAssetsExcludingCapitalizedSoftwareCostsInDevelopmentStageNet" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_IndefiniteMember" abstract="true" name="IndefiniteMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_TemporaryEquityAmortizationShares" abstract="false" name="TemporaryEquityAmortizationShares" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="sncr_MonthlyPercentageAfterApplicableAnniversaryMember" abstract="true" name="MonthlyPercentageAfterApplicableAnniversaryMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_CapitalizedSoftwareAndPatentsMember" abstract="true" name="CapitalizedSoftwareAndPatentsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_STINMember" abstract="true" name="STINMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_RisksAndUncertaintiesPolicyTextBlock" abstract="false" name="RisksAndUncertaintiesPolicyTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="sncr_DebtInstrumentRedemptionPrice" abstract="false" name="DebtInstrumentRedemptionPrice" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="sncr_VestingFirstAnniversaryMember" abstract="false" name="VestingFirstAnniversaryMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_PurchaseObligationToBePaidAfterYearThree" abstract="false" name="PurchaseObligationToBePaidAfterYearThree" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_ContractAcquisitionCostsMember" abstract="true" name="ContractAcquisitionCostsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsAdjustmentInPeriod" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsAdjustmentInPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="sncr_ConvertibleSeniorNotesDue2019Member" abstract="false" name="ConvertibleSeniorNotesDue2019Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_TheSecuritiesLawActionsMember" abstract="true" name="TheSecuritiesLawActionsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_SilverPrivateHoldingsILLCMember" abstract="true" name="SilverPrivateHoldingsILLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_LeaseLiabilityNoncurrent" abstract="false" name="LeaseLiabilityNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_UponAchievementOfPerformanceObjectivesMember" abstract="true" name="UponAchievementOfPerformanceObjectivesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_TemporaryEquityPaymentOfPreferredDividend" abstract="false" name="TemporaryEquityPaymentOfPreferredDividend" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_PreferredStockDividendRatePercentageThree" abstract="false" name="PreferredStockDividendRatePercentageThree" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_ScheduleofForeignCurrencyGainsLossesTableTextBlock" abstract="false" name="ScheduleofForeignCurrencyGainsLossesTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="sncr_DisposalGroupIncludingDiscontinuedOperationEscrowDeposit" abstract="false" name="DisposalGroupIncludingDiscontinuedOperationEscrowDeposit" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_ShareRepurchaseProgram2016Member" abstract="false" name="ShareRepurchaseProgram2016Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_CapitalStockParOrStatedValuePerShare" abstract="false" name="CapitalStockParOrStatedValuePerShare" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="sncr_OtherComprehensiveIncomeNetGainLossOnIntraEntityForeignCurrencyTransactionsArisingDuringPeriodNetOfTax" abstract="false" name="OtherComprehensiveIncomeNetGainLossOnIntraEntityForeignCurrencyTransactionsArisingDuringPeriodNetOfTax" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_SequentialTechnologyInternationalLLCAndAPCapitalHoldingsIILLCMember" abstract="true" name="SequentialTechnologyInternationalLLCAndAPCapitalHoldingsIILLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_DeferredTaxLiabilitiesBasisDifferences" abstract="false" name="DeferredTaxLiabilitiesBasisDifferences" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract" abstract="true" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageRemainingContractualTermAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="sncr_DebtInstrumentProceedsFromSaleOfStockTransactionsUsedForRedemptionOfSharesAndBuyBackOfShares" abstract="false" name="DebtInstrumentProceedsFromSaleOfStockTransactionsUsedForRedemptionOfSharesAndBuyBackOfShares" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_DebtFloorInterestRate" abstract="false" name="DebtFloorInterestRate" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_StockIncentive2010PlanMember" abstract="true" name="StockIncentive2010PlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_OperatingLeaseRightofUseAssetNoncurrent" abstract="false" name="OperatingLeaseRightofUseAssetNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_TemporaryEquityDividendsShares" abstract="false" name="TemporaryEquityDividendsShares" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="sncr_DeferredTaxAssetsCredits" abstract="false" name="DeferredTaxAssetsCredits" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_SeniorNotesDueJune302026Member" abstract="true" name="SeniorNotesDueJune302026Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_EffectiveIncomeTaxRateReconciliationRegulatoryMattersPercent" abstract="false" name="EffectiveIncomeTaxRateReconciliationRegulatoryMattersPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_CumulativeAdjustmentToReceivable" abstract="false" name="CumulativeAdjustmentToReceivable" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_DebtInstrumentSalesAgentCompensationPercentage" abstract="false" name="DebtInstrumentSalesAgentCompensationPercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_SucceedingFirstYearPeriodMember" abstract="true" name="SucceedingFirstYearPeriodMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_AnnualPercentageAfterAchievementOfPerformanceObjectivesMember" abstract="true" name="AnnualPercentageAfterAchievementOfPerformanceObjectivesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_DeferredTaxAssetsLeaseObligations" abstract="false" name="DeferredTaxAssetsLeaseObligations" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_TemporaryEquityAmortization" abstract="false" name="TemporaryEquityAmortization" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_TemporaryEquityStockIssuedDuringPeriodSharesNewIssues" abstract="false" name="TemporaryEquityStockIssuedDuringPeriodSharesNewIssues" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="sncr_DisposalGroupIncludingDiscontinuedOperationRevenueTargetsToBeReceived24MonthsFromClosingDateContingentConsideration" abstract="false" name="DisposalGroupIncludingDiscontinuedOperationRevenueTargetsToBeReceived24MonthsFromClosingDateContingentConsideration" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_AccumulatedNetGainLossOnIntraEntityForeignCurrencyTransactionsMember" abstract="true" name="AccumulatedNetGainLossOnIntraEntityForeignCurrencyTransactionsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_DebtInstrumentContingentConsiderationLiability" abstract="false" name="DebtInstrumentContingentConsiderationLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_EffectiveIncomeTaxReconciliationBaseErosionAntiAbuseTaxPercent" abstract="false" name="EffectiveIncomeTaxReconciliationBaseErosionAntiAbuseTaxPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_DigitalMember" abstract="true" name="DigitalMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_NumberOfElectedClassTwoDirectors" abstract="false" name="NumberOfElectedClassTwoDirectors" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="sncr_DisposalGroupIncludingDiscontinuedOperationReceivable" abstract="false" name="DisposalGroupIncludingDiscontinuedOperationReceivable" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_ShareBasedCompensationArrangementByShareBasedPaymentAwardAggregateIntrinsicValueAbstract" abstract="true" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAggregateIntrinsicValueAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="sncr_SucceedingPeriodAfterTenYearsMember" abstract="false" name="SucceedingPeriodAfterTenYearsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_AssetsAndLiabilitiesLesseeTableTextBlock" abstract="false" name="AssetsAndLiabilitiesLesseeTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="sncr_SubscriptionServicesMember" abstract="true" name="SubscriptionServicesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_TemporaryEquityPreferredStockRedemptionShares" abstract="false" name="TemporaryEquityPreferredStockRedemptionShares" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="sncr_SoftwareDevelopmentCostsTableTextBlock" abstract="false" name="SoftwareDevelopmentCostsTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="sncr_DXPBusinessMember" abstract="true" name="DXPBusinessMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_OperatingLeaseRightOfUseAssetAbstract" abstract="true" name="OperatingLeaseRightOfUseAssetAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="sncr_EquityIncentivePlan2015Member" abstract="true" name="EquityIncentivePlan2015Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_EffectiveIncomeTaxRateReconciliationJointVenturePercent" abstract="false" name="EffectiveIncomeTaxRateReconciliationJointVenturePercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_PreferredStockDividendRatePercentageTwo" abstract="false" name="PreferredStockDividendRatePercentageTwo" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="sncr_AdjustmentsToAdditionalPaidInCapitalStockIssuedCommonStockIssuanceCosts" abstract="false" name="AdjustmentsToAdditionalPaidInCapitalStockIssuedCommonStockIssuanceCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="sncr_CustomerListsAndRelationshipsMember" abstract="true" name="CustomerListsAndRelationshipsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_SucceedingSecondYearPeriodMember" abstract="false" name="SucceedingSecondYearPeriodMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="sncr_AuditInformationAbstract" abstract="true" name="AuditInformationAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="sncr_DebtInstrumentParValue" abstract="false" name="DebtInstrumentParValue" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
</xs:schema>
