The -TNT Internet Control Option for -B Units

The -TNT option "internet-enables" Avtech pulse generators by adding a standard Ethernet 100 Mb/s port to the rear panel, in addition to the IEEE-488.2 GPIB and RS-232 ports normally found on "-B" units.

With the -TNT option, a user can plug the instrument into their local area network (LAN), and send commands using a web browser, or through a Telnet session. Web browsers and Telnet client programs are included with most modern operating systems, including Windows 2000, Windows XP, Linux, and Unix.

The SCPI-compliant command set is the same as that used for GPIB and RS-232 control, and is fully described in the programming manual.

RS-232 and GPIB cable lengths are normally limited to 20 meters (60 feet) or less - but Web and Telnet sessions can be established across the world, using standard LAN and Internet connections! RS-232 and GPIB remote control schemes typically force the user to use one particular computer (for instance, one with a GPIB controller card), but Web and Telnet sessions can be established from any computer on the same network!

Figure 1. Photo of the LAN (Ethernet), IEEE-488.2 GPIB, and RS-232 ports on a Model with the -TNT Option

A password is required to establish a Telnet session or to load the controlling web page. The password can be reset from the front panel, if required. The -TNT option uses the Dynamic Host Configuration Protocol (DHCP) to obtain its network address. A DHCP server must be present on the local network for the -TNT option to operate properly. If a DHCP server is not present on your network, consider using an inexpensive firewall box from D-Link, Linksys, Netgear or others between the Avtech instrument and the network. These firewall devices typically include a DHCP server feature. The firewall can also be used to limit access to the Avtech instrument to appropriate sections of your network.

Figure 2. Screenshot of a telnet session from a Linux-based computer

Figure 3. Example of Web-Based Control, on a Windows 2000 PC

LabView users can write Telnet-enabled control programs using one of two methods. The simplest method is to purchase the National Instruments LabVIEW Internet Toolkit, which provides simple VIs to establish telnet sessions. The other method is less costly but slightly more complicated, and uses the "System Exec.vi" to run a telnet client program. See the National Instruments KnowledgeBase article, How Can I Use the Telnet Communications Protocol With National Instruments Software? for details.