REG Design |
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Three Devices
The Global Consciousness Project uses three different random event
generators (REG or RNG). These are
the PEAR portable REG, the
Mindsong Microreg, and the Orion RNG.
In all cases, the design begins with white noise, for example in the PEAR Portable REG, a flat spectrum +/- 1 dB from 1100 Hz to 30 kHz. A low end cutoff at 1000 Hz eliminates frequencies at and below the data-sampling rate. This filtering, together with appropriate amplification and clipping, produces an approximate square wave with unpredictable temporal variation. Sampling at a constant 1 kHz rate is typical, although special sources have been constructed allowing higher rates (up to 2 MHz). Analog and digital processes are completely isolated by alternating these operations to exclude contamination of the analog noise train by digital pulses.
The XORTo eliminate biases of the mean that might arise from such environmental stresses as temperature change, electromagnetic fields, or component aging, an exclusive or (XOR) mask is applied to the digital data stream. This is either an alternating 1/0 pattern (this is applied by the GCP software for the Orion devices, and in hardware for the PEAR devices) or a more complex mask comprising an array of all bytes with equal occurrence of 1/0 (this is in firmware in the Mindsong devices). Both types of XOR exclude bias of the mean, in principle, and the latter also excludes all short-lag bit-to-bit and byte-to-byte autocorrelations. Finally, data for the GCP are recorded as "trials" that are the sum of 200 bits drawn from the primary bit sequence. This sum across bits further mitigates any residual short-lag autocorrelations or other time-series predictability. The result is a data sequence of random numbers that conform to the appropriate theoretical binomial distribution and to its normal approximation. The final output of the physical REG unit is a sequence of bytes presented to the computer's serial port, which are then formed by the acquisition software into a sequence of trials (sums of 200 bits), generated at 1 per second. This composite trial value, based on an N of 200 bits has an expected mean of 100 and standard deviation of Sqrt(50). Calibrations on all of the devices show behavior that closely models theoretical expectations for mean, variance, skew and kurtosis. The calibration suite includes tests for runs, autocorrelation at raw and 50-trial block levels, conformance to the Arcsine distribution, and a number of other statistical criteria.
"Orion's Random Number Generator consists of two independent analogue Zener diode based noise sources. Both signals are converted into random bitstreams, combined [using an XOR] and subsequently transmitted in the form of bytes to the RS-232 port of your computer. Special timing circuits ensure that crucial logical operations occur at moments that the device has stable signals. The baud rate is 9600. So the device is capable of supplying you with about 960random bytes or 7600 random bits per second Power is drawn from the RTS and TXD signal. (pins 4 and 2 of the D-25connector). In order to work properly the RTS signal should be high (5 volts or higher) and one should not send bytes to the device!" A version of this page with some links to background material is available at REG experimental design. A question that may be relevant for use of these well-designed devices is whether they might be affected by power line influences. Use of the REG/RNG devices in the GCP networkIn the EGG project, any of the three devices, PEAR, Orion, MicroREG, may be used. In the application, they are functionally indistinguishable, although the EGG software configuration must specify which device is in use. In addition to the technical details of the device construction and operation, an adequate picture of the overall project requires a description of the physical data-acquisition system, and definition of the terms used for the specialized equipment. At each of a growing number (about 40 in late 2001; over 60 in 2005) of host sites around the world, one of these well-qualified sources of random bits (REG or RNG) is attached to a computer running custom software to collect data continuously at the rate of one 200-bit trial per second. This local system is referred to as an "egg," and the whole network has been dubbed the "EGG," standing for "electrogaiagram," because its design is reminiscent of an EEG for the earth. (Of course this is just an evocative name; we are recording statistical parameters, not electrical measures.) The egg software regularly sends time-stamped, checksum-qualified data packets (each containing 5 min of data) to a server in Princeton. We access official timeservers to synchronize all the eggs to the second, to optimize the detection of inter-egg correlations. Occasional drifts occur, but any mis-synchronization is expected to have a conservative influence in our standard analyses. The server runs a program called the "basket" to manage the archival storage of the data. Other programs on the server monitor the status of the network and do automatic analytical processing of the data. These programs and processing scripts are used to create up-to-date pages on the GCP Web site, providing public access to the complete history of the project's results. The raw data are also made available for download by those interested in checking our analyses or conducting their own assessments of the data. Each day's data are stored in a single file with a header that provides complete identifying information, followed by the trial outcomes (sums of 200 bits) for each egg and each second. With 40 eggs running, there are well over 3 million trials generated each day, and the complete database at the end of 2001 occupies approximately 3 gigabytes of storage in a highly compressed form. A thorough analysis of the data has been done for the Analysis 2004 project. This includes detailed assessment of the performance of the individual devices and a description of the normalized random data used in our rigorous formal analysis. A good general reference on theory and practice of random number generation is at PLAB. |