# ITU-T G.8273.2 (T-BC and T-TSC) One-Page Summary

**Title: ***Timing characteristics of Telecom Boundary Clocks (T-BC) and Telecom Slave Clocks (T-TSC)*

*Timing characteristics of Telecom Boundary Clocks (T-BC) and Telecom Slave Clocks (T-TSC)*

**Summary**

Clock specification for T-BC (boundary clock) and T-TSC (time slave clock) for full timing support architecture, including noise tolerance, noise generation, noise transfer, phase transients

Four clock types defined, classes A to D:

Class A intended for short chains (up to 10 clocks), to meet ±1.5µs overall requirement

Class B intended for long chains (up to 20 clocks) , to meet ±1.5µs overall requirement

Class C intended for long chains (up to 20 clocks), to meet ±130ns overall requirement

Class D intended for long chains, delivered over new interface types (e.g. FlexE, FlexO) with special provision for low-noise timing transmission

**Status**

Current version:

, plus**2nd. Edition, January 2017**and**Amd. 1, August 2017****Amd. 2, January 2019**Download from: http://www.itu.int/ITU-T/recommendations/rec.aspx?rec=13109

**Key Contents**

**Noise Generation:**

Parameter | Conditions | Class A | Class B | Class C | Class D |
---|---|---|---|---|---|

Max |TE| | Unfiltered, 1000s | 100ns | 70ns | 30ns | - |

Max|TE_{L}| | 0.1Hz low-pass filter,1000s | - | - | - | 5ns |

cTE | Averaged over 1000s | 50ns | 20ns | 10ns | - |

dTE_{L} MTIE | 0.1Hz low-pass filter, Const. temp, 1000s | 40ns | 40ns | 10ns | - |

0.1Hz low-pass filter, Var. temp, 10000s | 40ns | 40ns | - | - | |

dTE_{L} TDEV | 0.1Hz low-pass filter, Const. temp, 1000s | 4ns | 4ns | 2ns | - |

dTE_{H} | 0.1Hz high-pass filter, Const. temp, 1000s | 70ns | 70ns | - | - |

**Transfer Function:**

**Simplified Functional Model:**

**On this page:**