Model: MC-1-M (2U)
Doc. Ref. no. : m05/om/101
Issue no. 14
User’s Manual
Page 72 of 103
11.2.2.7.1
Connecting IRIG-B DCLS:
To drive multiple load from IRIG-B DCLS output connect all end devices in parallel. To determine load
current for one IRIG-B DCLS output
•
Determine no of load devices to be connected
•
Determine input impedance of each load devices (Rdev)
•
Calculate load current of each device (Idev = 5V ÷ Rdev)
•
Sum all the load device current and compare with model MC-1-M load capacity current
GPS Master Clock model MC-1-M IRIG-B DCLS time code output impedence is 50
Ω
@ 5V.
11.2.2.7.2
Connecting IRIG-B AM:
The main difference in computing the load capacity for IRIG-B AM and IRIG-B DCLS is that some of the
modulated IRIG-B decoders are sensitive to the peak-to-peak voltage. Connecting multiple devices with
MC-1 IRIG-B AM output causes increase in current flow which affects the Pick-Pick output voltage to
decrease. GPS Master Clock MC-1-M IRIG-B AM Time code signal output impedance is 100
Ω
.
11.3
Timing Output – NTP
11.3.1 NTP Introduction:
NTP (Network time protocol) is a common method for synchronization of hardware clocks in local and
global Ethernet networks. The software package NTP is an implementation of the actual version 3, based
on the specification RFC-1305. NTP protocol is used to synchronize and maintain the time among
distributed networks of servers and clients. NTP protocol is evolved from Time protocol but is designed to
maintain accuracy and robustness even on the networks involving multiple gateways, high network path
delays and unreliable nets. NTP protocol is applied on the application layer on UDP based IP layer.
The purpose of NTP is to convey timekeeping information (in terms of UTC) from NTP servers to other
time clients via the Internet and also to cross-check clocks and mitigate errors due to equipment or
propagation failures. In NTP basic model, NTP client device sends the NTP packet message over wire to
NTP server (time source) at prefixed/defined interval (as per NTP standard). The NTP server
interchanges IP addresses and ports, overwrites certain fields in the message, inserts current timestamp
in packet, recalculates the checksum and returns the message immediately to NTP client. Information
included in the NTP message allows the client to determine the server time with respect to local time and
adjust the local clock accordingly. After NTP message is received, NTP client calculates time offset, own
local clock frequencies and update in its database at regular intervals to maintain the clock time
synchronization with NTP server time. This may result in either a step-change or a gradual phase
adjustment in time of the NTP client’s local clock to reduce the offset to zero or as minimum as possible.
The accuracies achievable by NTP client depend strongly on the precision of the local-clock frequency
and stringent control of device and process latencies.
NTP architecture model consists of number of primary reference sources, synchronized by wire or radio
clock. There are other several multiple secondary time sources/clients which are arranged in hierarchal
manner in network which request time from primary reference sources. Under normal circumstances it is
intended that the synchronization subnet of primary and secondary servers assumes a hierarchical-
