GPS / GNSS / NavIC Time Servers
Primary Reference Clock

VCL Products > GPS / GNSS Time Servers > VCL-2156-EXT: NTP Time Server
NTP Client / NTP Slave
NTP Client / NTP Slave
NTP Client / NTP Slave
NTP Client / NTP Slave - Front
NTP Client / NTP Slave
NTP Client / NTP Slave - Back

VCL-2156-EXT, NTP TIME SERVER, GPS / GNSS / NavIC
Primary Reference Clock (G.811)

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The VCL-2156-EXT is a NTP Server and a ITU-T G.811 Primary Reference Clock, designed to deliver highly accurate time and frequency synchronization with user-selectable interface options. It locks to GPS / GNSS / NavIC references and provides NTP services to private networks such as Railways and Metro ticketing and platform systems, Airports and Air Traffic Control facilities, Electric Sub-Stations, Power Distribution and Transmission companies, Oil and Gas Utilities, ISPs, Cable TV networks, and Campus networks that require complete isolation from public networks for security reasons. Semi-modular GPS clock offering multiple factory-configured IRIG-B and 1PPS output options, ensuring reliable and stable time synchronization for critical applications.

VCL-2156-EXT NTP Server is a dual-band GPS clock supporting L1 (GPS, GNSS, Galileo) and L5 (GPS, Galileo E5a, NavIC) signals. Its dual-frequency design ensures high accuracy, reliability, and resilience. Multipath Mitigation with Dynamic Satellite Selection maintains signal integrity in difficult conditions. Ideal for telecom, power grids, data centres, and defence, it provides precise, uninterrupted synchronization with stable outputs from multiple constellations.

Using two frequency L1 and L5 bands makes the clock less vulnerable to jamming or spoofing of a single frequency. The receiver can switch to the other frequency band in case one is compromised by such attacks. Provides better continuity of service for critical infrastructure. VCL-2156-EXT locks to a GPS / GNSS / NavIC reference to provide an NTP time reference on up to 4+1, 10/100BaseT Ethernet Ports which can be segregated to serve separate classes of assets in the network.

NTP Peering:

NTP peering is a method to allow multiple NTP servers to share time. Having more than one reference server configured increase's reliability of the NTP server. In peering mode, in addition to its GPS reference, VCL-2156-EXT can be configured to receive and monitor time from an additional Stratum 1 NTP Server available on the network. This allows the unit to fall back to its peer source in the event its primary reference becomes unavailable.

Performance:

The VCL-2156-EXT has 4+1, 10/100 BaseT Industrial Ethernet Ports that meet and comply with “Power Contact and Lightening Protection” as per EN61000-4-5 Level 3 specifications making it suitable for the equipment to be installed in harsh industrial environments which include Electric Sub-Stations, Railway and Metro Networks. VCL-2156-EXT provides a better than 30 nanosecond accuracy to assure high bandwidth NTP Performance of better than 7,500 NTP requests per second (40,000 NTP Slaves supported).

Security Features and Capabilities:

  • MD5/SHA1 authentication for secured NTP access
  • Key management for NTP clients
  • Option to disable clear text (Telnet) for secure communication
  • Supports Secure Shell (SSH) network protocol for encrypted communication
  • Supports RADIUS server for secure authentication and access control
  • Supports user-configurable Ethernet port protection
  • Supports NTP Peering for creating a redundant NTP server
  • Encrypted Password Control to access the device
  • Password Strength Monitoring
  • Alert notifications using secure SNMPv3 traps

Holdover (G.812) Synchronization:

  • OCXO (Double Oven-Controlled Crystal Oscillator)
  • OCXO Stability: ± 3ppb
  • Accuracy
    • One day Aging is ± 0.4ppb
    • 20Year Aging is ± 80ppb
Input: GPS / GNSS / NavIC, NTP and 1PPS
Outputs: NTP, 2.048MHz, 2.048MBits (E1), 10MHz, 1PPM/1PPH, 1PPS, 1PPS Adj, ToD NMEA 0183, IRIG-B (Unmodulated BNC and Modulated RJ45, Unmodulated DCLS - RS232, RS485, AM RJ45, ST - Optical), 1PPS BNC and ST - Optical, ToD, NMEA 0183, 4 User selectable time and PPS output modules.
Power Supply: 1+1 Power Supply option, 24V DC, 48V DC, 110-220V DC, 110-240V AC, 50/60 Hz
Power Consumption: < 10W at ambient (steady state 24°C)

Features and Highlights

  • GPS / GNSS / Galileo / NavIC Input (TNC)
  • External Inputs: 1PPS (SMA), NTP (RJ45)
  • Functions as a Primary NTP Server
  • Support Anti-jamming and Anti-spoofing
  • Automatic failover to function as a secondary NTP Server, in the absence of GPS Signal
  • High bandwidth NTP performance
  • Upto 7,500 NTP requests per second
    • 40,000 NTP Slaves supported
    • 250,000 SNTP Slaves supported
  • Multiple NTP Ports - 4+1 x Independent 10/100 Mbit/s, RJ-45 Ethernet interfaces
  • ITU-T G.811 / Stratum 1 compliant (PR) Primary Reference when locked to GPS / GNSS / NavIC
  • ITU-T G.812 compliant holdover (OCXO)
  • Synchronization of NTP / SNTP clients
  • Supports Unicast, Multicast, Broadcast
  • NTP Peering (1+1 redundant NTP Server)
  • Leap Second correction Support
  • MD5 / SHA1 authentication for NTP clients
  • 1 x IRIG-B Un-Modulated DCLS (BNC)
  • 1 x IRIG-B Modulated AM (RJ45)
  • Meets and comply with Power Contact and Lightening Protection as per EN61000-4-5 Level 3 specifications.
  • Alert notifications via SNMP Traps, SNMPv2, SNMPv3, SMTP (Email)
  • Concurrent IPv6 and IPv4 operation
  • Supported network protocols: IPv4, IPv6, SSH, TELNET, FTP, SYSLOG, SCP, SFTP, TCP, UDP and DHCP
  • Secure network management: enable or disable options
  • DC, or AC, or 1+1 Redundant AC+DC Power Supply options.
  • Multi service platform - User selectable output modules, upto 9 User selectable output modules.

Synchronization Inputs:

  • 1 x GPS / GNSS / NavIC (TNC)
  • 1x 1PPS (SMA)
  • NTP Time Source (RJ45)

NTP Outputs:

  • 4 x 10/100Mbps NTP / SNTP Interfaces
  • 1 x 10/100Mbps user configurable NTP / SNTP interface

GPS/GNSS Receiver Specifications:

  • 50 Channel GPS Receiver
  • 62 Channel GNSS Receiver
  • GPS, GNSS, Galileo L1 (1575.42 MHz) frequency, C/A Code Receiver
  • GPS, Galileo-E5a, NavIC L5 (1176.45 MHz) frequency, C/A Code Receiver
  • Tracks up to 32 satellites with Multiple Constellation.
  • Synchronizing Time:
    • Acquisition time - Hot Start: 1 sec.
    • Acquisition time - Warm Start: 28 sec.
    • Acquisition time - Cold Start: 28 sec.
  • GPS / GNSS / NavIC Signal
    • Tracking and Navigation: -165 dBm
    • Reacquisition -160 dBm
    • Cold Start -148 dBm
  • Antenna Connector: TNC
  • Accuracy Of Time-Pulse Signal referenced to GPS: ± 30ns (raw)
  • Accuracy Of Time-Pulse Signal referenced to GNSS: ± 20ns (raw)
  • Accuracy Of Time-Pulse Signal referenced to GPS/GNSS: ± 15ns (compensated)
    (Note: with all satellites in view at -130db)

Network Time Protocol:

  • NTP v2, (RFC 1119), NTP v3 (RFC 1305), NTP v4, (RFC 5905), SNTP v3 (RFC 1769), SNTP v4 (RFP 2030), MD5/SHA1 Authentication
  • Upto 7,500 NTP requests per second
  • 40,000 NTP Slaves supported
  • 250,000 SNTP Slaves supported
  • Internet Protocol: IPv4/IPv6
  • NTP version 4.2.8p7
  • Time Protocol: TIME (RFC 868)
  • Daytime Protocol: DAYTIME (RFC 867)
  • Supports Unicast, Multicast and Broadcast
  • NTP Peering

Local / Remote Management:

  • RS-232C (DB-9)
  • USB Serial
  • 10/100BaseT Ethernet RJ45
  • 1 x External Alarm Relay Contact.
  • Telnet / SSH (option to disable clear text communication to comply with NERC security requirements)
  • CLI Control Interface (Tera Term or putty)
  • SNMPv2, SNMPv3 Traps (MIB provided)
  • Syslog, HTTP, HTTPS, TCP, UDP, FTP, SCP, SFTP.

Display:

  • LCD-display with back-light (HH: MM: SS) - 12/24 Hour Mode, number of satellites with selected Constellation.

Application Diagram



NTP Time Server with IRIG-B Outputs

The NTP Server is available with three GNSS configuration options, allowing customers to select the most suitable model based on operational, security, and resilience requirements.

Option #1 – GPS (L1):
  • Supported Satellite Constellation: GPS only
  • Frequency Band:
    • L1-1575.42 MHz (GPS)
  • Suitable for standard timing applications where single-constellation GPS support is sufficient.
Option #2 – Dual-Band Multi-GNSS Clock with Jamming & Spoofing Detection:
  • Supported Satellite Constellations: GPS, Galileo (E5a), NavIC
  • Frequency Bands:
    • L1-1575.42 MHz (GPS, Galileo)
    • L5-1176.45 MHz (GPS, Galileo E5a, NavIC).
  • Features:
    • GNSS jamming detection alerts
    • GNSS spoofing detection alerts
    • Suitable for critical infrastructure applications requiring enhanced reliability and signal monitoring.
Option #3 – Dual-Band Multi-GNSS Clock with Anti- Jamming & Anti-Spoofing:
  • Supported Satellite Constellations: GPS, GLONASS, Galileo (E5a), NavIC
  • Frequency Bands:
    • L1-1575.42 MHz (GPS, GLONASS, Galileo)
    • L5-1176.45 MHz (GPS, Galileo E5a, NavIC).
  • Features:
    • Advanced anti-jamming protection
    • Advanced anti-spoofing mechanisms
    • Robust signal validation and interference detection
    • Automatically switching to the other band if any one band is jammed to maintain satellite lock and provide the alert.
    • Designed for high-security and mission-critical environments requiring maximum GNSS resilience.

Note: All NTP Server configuration options support the same INPUT and OUTPUT interfaces, protocols, and timing outputs. The differences between the options are limited only to the supported GNSS constellations and security features.