Siemens SINAUT ST7 System Manual page 277

DCF77 radio clock
DCF77 is a time signal transmitted on the normal frequency 77.5 kHz as encoded time
information. Reception of the time signal is restricted to Western Europe.
Some TIM variants (TIM 4VD, TIM 42D, TIM 43D, TIM 44D, TIM 4RD) are equipped with a
DCF77 receiver module that can receive the DCF77 time signal either over an indoor or
outdoor antenna. The ST7 time management currently requires the existence of a DCF77
time signal to allow time synchronization of the stations and the control center throughout a
network.
For applications that cannot receive the DCF77 time signal, SINAUT provides a GPS
receiver module with a GPS outdoor antenna that converts the GPS Time signal for the
DCF77 receiver module.
Direct data communication
Communication between two stations. In dial-up networks or in Ethernet, this is achieved by
direct connection establishment between the two stations. On dedicated lines and in wireless
networks or in GPRS mobile wireless service or when using the MSC protocol, direct
communication is more "indirect". It is switched via the closest → master TIM.
DSL
Digital Subscriber Line
DSL is used mainly for transmission of telephone and Internet data. By using a higher
bandwidth, data can be transmitted at transmission speeds in the two to three figure Mbps
range.
Ethernet / Industrial Ethernet
Industrial Ethernet is a powerful communication network complying with the international
standard IEEE802.3 (Ethernet) that was optimized to meet the requirements of industrial
application. Ethernet is designed with a linear or star topology. The transmission media are
shielded coaxial cables, twisted pair, or fiber-optic cables. SIMATIC NET Industrial Ethernet
uses both the Ethernet and Fast Ethernet standards.
Ethernet TIM
TIM
→
Firewall
A firewall is a network component via which a secure network can be linked with an
unsecure network. The task of a firewall is to control data exchange between the networks.
General request (GR)
With a general request, subscribers in a SINAUT network can request a current process
image from their communications partners. This happens automatically when a disrupted
connection has been restored or when a failed partner reports a restart. Apart from the
Station control system
System Manual, 07/2009, C79000-G8976-C178-07
Glossary
277