In the electronic version of the trapping system, two identical (as far as practically realizeable) transfer function amplifiers were constructed. The trap size and piecewise linear breakpoints were controllable by 10 turn potentiometers with scales, 1% accuracy, and the settings were precise to 1 part in 1000 of full scale. Two sample-and-hold circuits, externally clocked, transfer the output values to the input on a clock edge. Thus one starts from two uncoupled chaotic trap systems with variables called, say, u and v at the inputs and w and z at the respective outputs. A circuit simulates a rotation matrix which takes part of the output w, adds and subtracts it to part of z, and applies the resulting two outputs to the inputs u and v via the sample-and-hold circuits.
There are some details here concerning setting the ranges of the variables, and the additional contraction of the mapping produced by the rotation circuitry needs to be zero. There is no space to discuss these. Experimentally, this two-dimensional system takes (as might be expected) longer to trap for a trap having a given size within one of the transfer characteristic circuits. However, the added noise need only release the system from the trap in one branch or dimension. Thus the probability of untrapping is very nearly the same as for a 1-dimensional version. The tape played is taken from this two dimensional trap. No extra noise has been added above the inherent circuit noise.