# Time-alignment validation boundary Canonical URL: https://eloragrid.ai/symbols/time-alignment-validation-boundary Publisher: Elora Grid Updated: 2026-11-03 Lookup label: TVB Drawing use: Schematic Reference families: Manufacturer Representation: Functional block Installation focus: substations Input: Reference and client timing points Output: Timing comparison information Identifies the source and client timing points included in the defined synchronization assessment. ## In plain English ### What this block does Identifies the source and client timing points included in the defined synchronization assessment. ### A simple example In a substation, a station clock can provide precision timing to process equipment and another timing interface to event recorders. The alarm system should distinguish loss of a distribution path from loss of the external time source. For this reference, the drawing identifies “Reference and client timing points” at the input and “Timing comparison information” at the output. The drawing does not establish measured timing performance. ### What the drawings help you do Start at the named input: Reference and client timing points. Identify its source device or document and the state represented on the drawing. Follow the named output: Timing comparison information. Cross-reference its destination and separate the command from confirmation that the equipment responded. ### Terms - Input: Reference and client timing points - Output: Timing comparison information - Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections. Concept diagram: Reference and client timing points → TVB → Timing comparison information A reading guide. The entry's original illustration and input/output facts describe this application. - [SEL-2488 satellite-synchronised network clock](https://selinc.com/products/2488/) ## What it represents Identifies the source and client timing points included in the defined synchronization assessment. A station time system provides a shared time reference for protection records, measurements and automation. Different devices can use different timing protocols, so the time source, distribution path and quality information must remain identifiable. In a substation, a station clock can provide precision timing to process equipment and another timing interface to event recorders. The alarm system should distinguish loss of a distribution path from loss of the external time source. For this reference, the drawing identifies “Reference and client timing points” at the input and “Timing comparison information” at the output. The drawing does not establish measured timing performance. Show the source and client of each time connection. Required accuracy, holdover, protocol profile and loss-of-time behavior follow the selected application; a common timestamp format does not guarantee synchronized events. The functional block is an independent explanation of this named application. Equipment-specific ratings, terminal connections and operating conditions must be established in the project documentation. ## How to read it - Start at the named input: Reference and client timing points. Identify its source device or document and the state represented on the drawing. - Follow the named output: Timing comparison information. Cross-reference its destination and separate the command from confirmation that the equipment responded. - The drawing does not establish measured timing performance. - Show the source and client of each time connection. Required accuracy, holdover, protocol profile and loss-of-time behavior follow the selected application; a common timestamp format does not guarantee synchronized events. ## Information to show or reference - Label the source and connection reference for reference and client timing points. - Identify the destination and defined state of timing comparison information. - Record the equipment or control-document revision supporting this functional block. - Check this application limit in the project design: The drawing does not establish measured timing performance. ## Important distinction The drawing does not establish measured timing performance. This reference describes the named application; it does not establish a new IEC graphical symbol, an ANSI device-function number or an exact manufacturer connection diagram. ## Facts - Representation: Functional block - Installation focus: Substations - Input / boundary: Reference and client timing points - Output / connection: Timing comparison information - Lookup label: TVB is a library lookup label, not a standard device designation. ## Public references - [SEL-2488 satellite-synchronised network clock](https://selinc.com/products/2488/) — SEL. Public technical context for substation timing and event interfaces. PTP, NTP, IRIG-B, pulse distribution, reference failover and timing quality. The application text and educational graphic are independently authored; the publisher does not certify this representation. ## Graphic scope Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.