NTP and Time Code Explained

NTP

Network Time Protocol (NTP) is an open standard Internet protocol that utilizes standard ethernet wiring to synchronize computers, clocks, networks and other systems to a NTP reference server. The signal can be transmitted over LAN and WAN wired networks and over various wireless systems.

There are numerous public sources of NTP available. Many universities and governmental agencies provide access to NTP servers although, because of the number of request, some of these facilities are limiting access and in some cases even charging access fees.

NTP service can be established on your internal network using a stand alone device such as the NTP100 which gets time from the atomic clocks in the GPS system and generates NTP. GPS receiver cards such as the GPSPCI along with NTP software in a computer on the network can also provide a local NTP reference source. In many cases because of firewalls and other network constraints a local NTP server is the recommended approach and in many cases provides a more accurate and available NTP.

Accuracy of time in a typical NTP installation will depend on many factors but is typically better than +/- 500 milliseconds or so.

Time Code

Time code is a low power audio signal similar to the signal of a modem that contains time and date information. This signal can be transmitted over inexpensive coaxial cable and wiring such as telephone pairs. It can be distributed much as audio wires can be connected in parallel to multiple speakers. With the proper distribution amplifiers, such as the TCA100, it can be sent over long distances and connected in parallel to hundreds of clocks and other devices. It is generally an inexpensive, robust and reliable means of distributing time and date around a local plant or operation.

With an accurate time code source such as the GPS200 and a time code reader card such as the TCR500 a local system can be synchronized to within 20 or 30 milliseconds limited by the software operating system.