March 4, 1998
Tualatin, Oregon USA

LinearX Systems is proud to announce the introduction of two new accessories for interfacing your analyzers to the outside world.

For dB Drag light towers:

First is a series of components to be interfaced for dB Drag Racing light towers setups. These components are a cost effective system that will connect to the pcRTA or other pc based real time analyzer and will control 2 sets of 24 lights for eye appealing, crowd gathering dB drag racing sport. The DBDR components consists of an interface card, power module, and connection cable.

The I/O interface is an 8-bit ISA bus card which is mounted in a PC computer. The unit provides 6 bytes of registers configured as (2) sets of three each. I/O port base address is selectable as 0300h or 0310h. Output drive can be True or Complement. Control power (GND or VCC) is also fed via two pins through the connector, along with the 48 output drive signals. All output signals are supplied through a 50 pin SCSI-II connector.

The power module provides 2 sets of 24 solid state relays (48 SSR's total) with a capacity of 2A/240VAC per circuit. Each set is wired as (3) groups of 8 circuits, with one common power input per group. The terminal blocks accept 12-18 ga stripped wire. The control input signals are supplied through a 50 pin SCSI-II connector, PCB mounted. The module is 12.5 inches x 5.0 inches, height less than 2.0 inches. Eight mounting holes are provided.

For Speaker Tweaks:

Second is a Voltage & Current Measurement Interface called the VI Box. The VI Box is a device to be used with almost any analyzer or meter to determine speaker impedance, speaker parameters, and measuring crossover components at any power level. You can also simultaneously measure impedance, SPL and power.

Precision measurement of loudspeaker impedance has always presented a unique set of problems. While the commonly used constant current source (CCS) method provides easy and quick impedance measurement, it sacrifices the quality and accuracy of the data. Loudspeakers are normally operated in a constant voltage source (CVS) mode, by direct connection to a power amplifier. For accurate impedance measurements CVS operation must be maintained during impedance measurement as well.

The VI Box is a device which provides all of the components, circuitry, and interface connectors necessary to make precision impedance measurement using the CVS method a snap. The VI Box provides binding post connectors for the amplifier and speaker cables, as well as two XLR signal line outputs for the load current (I) and load voltage (V). The VI Box is built entirely with 1% precision low TC components and features selectable 4-wire Kelvin shunts, a precision voltage divider, and balanced line output impedance.

Once the current flow through the load and the voltage across the load are measured, the true load impedance can be calculated using basic Ohm’s law as Z=V/I and the true power calculated as P=V*I. The VI Box can be used with almost any audio analyzer or meter including the LMS, TEF-20, AP System-1, and any other analyzer which provides a balanced line input. Dual channel analyzers are ideal for use with the VI Box since both current and voltage can be measured simultaneously.

Using the VI Box, impedance as well as SPL-can be measured simultaneously without the need of changes to the test setup or wiring. This is ideal for production line QC. Passive crossover components can be measured under actual load conditions as well. Many other valuable measurements are also possible including electrical distortion, temperature rise, TC, etc. If reliable and accurate loudspeaker parameters are the problem- VI Box is the answer.

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