VCL-2156, GPS NTP Time Server

Product Overview

The VCL-2156 NTP Time Server is designed to provide NTP output and ITU-T G.811 Primary Reference Clock that is locked to a GPS / GNSS reference to provide time synchronization to private networks such as Railways and Metro (ticketing and platform) networks, Airports and Air-Traffic Control facilities, Electric Sub-Stations, Power Distribution and Transmission companies, Oil and Gas Utilities, ISPs and Cable TV networks as well as to Campus networks that are required to maintain a complete isolation from public networks for security reasons. It may be also used by 2G, 3G and LTE service providers which provide a time of day reference to their customers over their wireless networks.

VCL-2156 locks to a GPS / GNSS 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.

The VCL-2156 is equipped with a highly accurate, low-noise OCXO to provide a high stability, ITU-T G.812, Type II, III compliant holdover clock with better than 12µs accuracy over a 24 hour (5 milliseconds per year) period in the event of unavailability of the GPS / GNSS signal, or GPS / GNSS antenna failure, or a temporary loss of reception in a totally isolated network without any external reference.

VCL-2156 establishes a highly accurate phase-synchronized frequency and time base by synchronizing to the GPS / GNSS satellite's atomic clocks to distribute synchronized time over packet based networks including Ethernet, Carrier Ethernet, IP and IP/MPLS Networks.

The VCL-2156 provides a wide range of GPS / GNSS referenced frequency and time sources that include 2.048MHz, 1/5/10MHz, 1PPS frequency as well as an NMEA and NTPv4 time reference. Features such as maintaining a distinctly separate IP address for system management and control, password based access, SSH as well as MD5 authentication ensures operational reliability and security. Additional features include remote login and remote firmware upgrade (file transfer) capabilities. VCL-2156 includes complete SNMP monitoring as well as support for enterprise directory services for user authentication, internal and external logging and monitoring of alarm and error messages through Syslog and e-mail alert ensures a high level of system manageability. Other features include DHCP for installation convenience and support concurrent IPv4/IPv6 support for future network up gradation.

Features and Highlights

  • GPS / GNSS time reference for SCADA applications
  • High bandwidth NTP performance
  • Upto 5000 NTP requests per second
  • 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
  • ITU-T G.812 compliant holdover
  • Synchronization of NTP and SNTP clients
  • Supports Unicast, Multicast and Broadcast
  • Leap Second correction Support
  • MD5 authentication for NTP clients
  • Supports 10000 NTP clients
  • 1 x IRIG-B Un-Modulated (BNC)
  • 1 x IRIG-B Modulated (RJ45)
  • Meets and comply with Power Contact and Lightening Protection as per Telcordia GR-1089-CORE and EN61000-4-5 Level 3 specifications
  • Alert notifications via SNMP Traps, SNMPv2, SNMPv3
  • Concurrent IPv6 and IPv4 operation
  • Supported networking protocols: IPv4, IPv6, SSH, TELNET, FTP, SYSLOG, SCP, SFTP
  • Secure network management: enable or disable options
  • Double Oven Quartz Oscillators (OCXO) hold-over
  • Stratum 1 when synchronized to GPS/GNSS, or Stratum 2 hold-over
  • DC, or AC, or 1+1 Redundant AC+DC Power Supply options.


VCL-2156 is designed to be deployed in concurrent IPv4 networks to provide NTP time and frequency synchronization.

The VCL-2156 has 4+1, 10/100 BaseT Industrial Ethernet Ports that meet and comply with “Power Contact and Lightening Protection” as per Telcordia GR-1089-CORE and 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 is powered by a high performance microprocessor and a highly precise GPS / GNSS based time receiver that provides a better than 30 nanosecond accuracy to assure high bandwidth NTP Performance of better than 5000 NTP requests per second.

Monitoring and Management

The configuration of the system can be managed by Graphical User Management Interface. Alternatively, a text based and menu driven setup utility can be started from the shell prompt after logging into the unit via Telnet or SSH. An optional Graphical User Network Management Interface (NMS) allows multiple systems installed on a networks to be monitored and configured from a single or multiple management locations.

Standards & Compliance

  • IEC - EMC – Certified to EN 55022: 2005 / CISPR 22, EN 55024:2005, IEC 61000-4-2
  • CE – 2001/95/EC, 2006/95/EC, EN60950-1, EN61000-6-2, EN61000-6-4
  • FCC – FCC Part 15 B Class A: Conducted Emission test on Power Line
  • FCC Part 15 B Class A: Radiated Emission >1 GHz FCC, 6 GHz, on Power Line

Application Diagrams

Application # 1:

NTP Server

VCL-2156, NTP Server

Application # 2: Assigning Multiple NTP Servers for high security applications and network segregation

Technical Specifications

GPS/GNSS Receiver Specifications:

  • 50 Channel GPS Receiver
  • 72 Channel GNSS Receiver
  • GPS L1 frequency, C/A Code Receiver
  • Tracks up to 12 satellites simultaneously
  • Synchronizing Time:
    • Acquisition time - Hot Start: Less than 1 sec.
    • Acquisition time - Warm Start: Less than 28 sec.
    • Acquisition time - Cold Start: Less than 28 sec.
  • GPS / GNSS Signal:
    • Tracking and Navigation: -162 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).

PTP Frequency and Time Outputs:

  • 1 x IEEE-1588 v2 PTP Grandmaster
  • 1 x 2.048 MHz, 75 Ohms, phase-locked to GPS (BNC). ITU-T G.811 compliant
  • 1 x 10 MHz, 50 Ohms, phase-locked to GPS BNC). ITU-T G.811 compliant
  • 1 x 1 PPS, phase-locked to UTC (BNC)
  • 1 x ToD (Time-Of-Day) output compliant to NMEA 0183 (DB9)
  • 1 x IRIG-B Un-Modulated (BNC-50 Ohms)
    (B000, B002, B003, B004, B005, B006, B007)
  • 1 x IRIG-B Modulated (RJ45)
    (B120, B122, B123, B124, B125, B126, B127)
  • 1 x 1 PPM / 1 PPH.

Network Time Protocol:

  • NTP v2, (RFC 1119), NTP v3 (RFC 1305), NTP v4, (RFC 5905), SNTP v3 (RFC 1769), SNTP v4 (RFP 2030), MD5 Authentication
  • Internet Protocol: IPV4 - DHCP (RFC 2131), IPV6 - DHCPv6 (RFC 3315)
  • NTP Version 4.2.8p7
  • Time Protocol: TIME (RFC 868)
  • Daytime Protocol: DAYTIME (RFC 867)
  • Communication: Unicast, Multicast, Broadcast
  • Synchronization of IEC-61850 Compliant.

Security and Protection:

  • Password Protection with password strength monitor
  • SSH.

Power Supply Options:

  • Dual Redundant
  • 1+1 AC power (100 to 240V AC, 50/60 Hz)
  • 1+1 DC 24V
  • 1+1 DC -48V
  • 1+1 DC 110~220V
  • AC or DC
  • Reverse Polarity Protection.

Antenna Specifications:

  • Antenna Type: Active, Wall Mounting
  • Polarization: Right hand circular
  • Frequency Band: 1575.42 MHz + 10 MHz
  • Amplifier Gain: 40dB + 4dB
  • VSWR: <2.0 Max, 1.0 Typical
  • Operating temperature: -40C to +85C
  • Out of Band Rejection: ≥ -60dB @ +50MHz off center (1575.42 MHz) frequency
  • Lightening Protection: According to EN61000-4-5 Level 3.
  • LMR400 (or equivalent) Cable Length - 30, 50, 60 and 90 meters.


  • Per MIL-HDBK-217F: ≥ 37 years @ 24C
  • Per Telcordia SSR 332, Issue 1: ≥ 42 years @ 24C