ITU-T G.8273.3 (T-TC) One-Page Summary
Title: Timing characteristics of Telecom Transparent Clocks (T-TC)
Summary
Clock specification for T-TC (transparent clock) for full timing support architecture, including noise tolerance, noise generation, noise transfer, phase transients
Two clock types defined, classes A and B
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
T-TCs are considered a direct replacement for T-BCs in the full timing support architecture, provided the T-TCs comprise no more than eight clocks in the overall chain (as per II.2.1 of G.8271.1)
Status
Current version: 2nd Edition, October 2020
Download from: http://www.itu.int/ITU-T/recommendations/rec.aspx?rec=13327
Key Contents
Noise Generation:
Parameter | Conditions | Class A | Class B |
|---|---|---|---|
Max |TE| | Unfiltered, 1000s | 100ns | 70ns |
Max|TEL| | 0.1Hz low-pass filter,1000s | - | - |
cTE | Averaged over 1000s | 50ns | 20ns |
dTEL MTIE | 0.1Hz low-pass filter, Const. temp, 1000s | 40ns | 40ns |
0.1Hz low-pass filter, Var. temp, 10000s | 40ns | 40ns | |
dTEL TDEV | 0.1Hz low-pass filter, Const. temp, 1000s | 4ns | 4ns |
dTEH | 0.1Hz high-pass filter, Const. temp, 1000s | 70ns | 70ns |
Transfer Function:
- No filtering of noise from PTP input to output
- Low-pass filtering of noise on physical layer frequency input, bandwidth between 1 and 10Hz
Holdover:
- No holdover provided by a T-TC
Simplified Functional Model:
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