# Industrial NTP Time Server — Selection Sheet (Reference · Policy · Capacity)

| Item | Content |
|------|---------|
| **Audience** | Agents / end customers / tender package |
| **Document title** | Selection Sheet (Reference · Policy · Capacity) |
| **Doc No.** | `DOC-TS1231-SEL-EN-011` |
| **Model** | **SY-1231-BG-T-S** / **SY-1231-GN-T-S** |
| **Document version** | 1.1 (this respin: hardware 1PPS, PULSE PPM; no IRIG / no OCXO) |
| **Firmware** | V4.9.0 (see device Web / label) |
| **Use** | Selection / bid / acceptance (status — policy — capacity one-pager) |
| **Companion** | Shipping Product Specification Product Specification (Shipping) in this folder |

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## 1. Reference source status

Time reference = **GNSS 1PPS + disciplined local clock** (not PTP; not dual-clock failover).

| Device state (Web / LCD) | Meaning | NTP under factory policy |
|--------------------------|---------|----------------------------|
| **LINK up** | Ethernet link OK | NTP / Web possible |
| **GNSS fix / satellites** | Module positioning valid | Discipline in progress |
| **Warm-up** (synced + PPS, not yet LOCK) | Cold-start converge | May reply **Stratum 2** |
| **LOCK** | Reference ready | **Stratum 1** |
| **Brief PPS loss** (after LOCK) | PPS blip window (~≤10 s) | May still reply |
| **Unlock / holdover** | GNSS or discipline lost | See §2 |
| **No LINK** | Cable / switch fault | **No** NTP |

**Do not mix layers:** internal/1PPS = **ns** parameters only; Ethernet NTP = **lab clause** (LOCK + low RTT → ms-class offset reachable; see report), **no** arbitrary-field guarantee; Modbus resolution **1 ms**.

| Channel | This SKU | Accept |
|---------|----------|--------|
| RJ45 NTP | Stratum 1 after LOCK | LAN client; not module-ns |
| RS-485 Modbus | UTC incl. ms | FC03 regs 10–16 |
| 1PPS OUT | 硬件缓冲 GNSS-edge fan-out (3.3 V) | Scope 1 Hz (probe the panel 1PPS jack only) |
| PULSE (4-pin Pin4) | 200 ms at UTC minute after LOCK (5 V) | Scope; mute if unlocked |
| **Not included** | **IRIG-B**, **OCXO**, PTP, dual Ethernet | Pick another SKU for timecode / µs holdover |

---

## 2. NTP serve policy (Web)

| Web name | LCD `Pol` | Warm-up | After LOCK | After GNSS unlock |
|----------|-----------|---------|------------|-------------------|
| **Lock-based (factory default)** | `LCK` | May **S2** | **S1** | **Stop** (except brief PPS blip) |
| **Lock + timed hold** | `TIM` | Same | **S1** | Still **S2** for ~**≤5 min** (preferred for Web export / soak) |
| **Holdover serve** | `HLD` | Sync → reply, usually **S2** | Usually **S2** | Continues (legacy “always need packets”) |

- Saved on **Network** page; persists across reboot.  
- Prefer **Lock + timed hold** during large Web CSV/HTML exports.  
- Optional **NTP ACL** is independent of the table above.

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## 3. Capacity (parameters + formula)

| Boundary | Spec | Note |
|----------|------|------|
| **NTP performance** | Overload protect ≤ **2048** req/s; **design reply capacity ≈ 1800 req/s (16 sources)**; **\(R\)** same as design reply | Parameters only; do **not** copy 10k-class appliance figures |
| **Planning cap** | **60** | Sales/SNMP; **≠** “must fill 60 at high poll” |
| **Client count** | \(N\le\min(60,\lfloor\eta\cdot R/f_{\mathrm{poll}}\rfloor)\) | \(\eta\) 0.5–0.7; customer computes from poll rate |
| **Per-source IP** | ≤ **8** replies/s | Anti-abuse |
| **During large Web export** | Global cap further derated | Shared single port with NTP |
| **Not included** | **IRIG-B**, **OCXO**, PTP (no third-party PTP license pack), dual-port failover, IPv6, NTP broadcast/multicast, NTS, **HTTPS**, SNMPv3 | Entry industrial NTP (**T** = TCXO); SNMP is v2c **read-only** |

**Acceptance:** After LOCK, LAN `w32tm` / `sntp` OK; Web **NTP Served** increases; do **not** accept “module ns” as “client ns”; offset per lab/contract method only.

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## 4. Quick answers

| Question | Answer |
|----------|--------|
| When is official Stratum 1? | **LOCK** under lock-class policy |
| Cold start with no time for clients? | Default allows warm-up **S2**; use **timed hold** for unlock behavior |
| How many clients? | **Compute from formula** (planning cap 60) — not a 10 k+ req/s appliance |
| Where does this sit? | **Entry cabinet NTP** — not PTP / not 10k-class room appliances |

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*Filename Selection Sheet. Interfaces: Industrial IF Protocol; operations: User Guide. Firmware as shown on device.*