A Newhall loop with exhaustive service, infinite buffer storage, and non-identical terminals is analyzed. A simple and computationally efficient procedure is demonstrated for determining first and second moments of queue lengths and scan times.

Optimum nonlinear receivers for digital signaling over channels with a relatively long impulse response become too complex to be practical. In this paper a suboptimum but simple and practical receiver is proposed for such channels. The receiver consists of a linear adaptive equalizer in cascade with a maximum-likelihood sequence estimator. A general method of finding the error probability of a maximum-likelihood sequence estimator (MLSE) in the presence of correlated noise is developed. An upper bound on the performance of an MLSE is also presented for the case when thc actual channel is different from the channel estimate known to the MLSE. The performance of the proposed receiver is analyzed and results of the analysis and computer simulation are shown for a typical telephone channel.

A simple experiment on a magnetically-balanced circuit, consisting of a flux source and two equal-length parallel paths is outlined. It is observed that if a controlling signal causes one of the parallel paths to be preferred and this controlling signal is removed before switching is completed, the parallel path originally preferred continues to be preferred. The core equivalent of a balanced circuit is then examined to determine if this phenomenon is present there as well. It is found that the basic behavior of a balanced circuit and its core equivalent can be made the same, provided care is taken in setting up the same initial conditions in both circuits. It is shown that initial flux levels are important, as well as the rate at which these initial levels are established. An attempt is then made to relate, in a qualitative way, the circuit properties observed to known properties of a single core. It is observed that the properties which will be exploited here are present in most standard materials; however, a balanced circuit tends to exaggerate these properties. In Section II experiments on two balanced circuits interconnected with a 1:1 turns ratio coupling winding are described. This configuration has been found to have two stable states, the final state being dependent on the initial condition in one of the elements. Signal amplification has been achieved over at least a 4:1 range of drive currents. These results are readily explainable by reference to the element characteristics described in the first section.

A correspondence has been established1between the topology of relay contact networks and the topology of magnetic circuits, which may be applied to a relay tree to produce a magnetic structure capable of generating, in a simple manner, all Boolean functions of N variables. Once the basic magnetic topology is established, it may be distorted to achieve winding simplicity at the expense of magnetic circuit complexity. In the resulting arrangement, the drive, hold (variable) and reset windings are always in the same position, regardless of the function to be generated. Any one of the 22Nfunctions of N variables is generated by linking a selected group of the output legs. The structure is such that all switching paths are of equal length, causing all outputs to be equal in amplitude. This balanced arrangement also permits the holding MMF to be significantly smaller than the drive MMF. The holding scheme is a symmetrical one, specifically arranged to overcome shuttle flux problems and reduce noise. An 8-leg manganese magnesium zinc ferrite structure is operated easily at a 4-μsec cycle time with an output of 500 mv into 5 ohms. The peak-signal-to-peak noise ratio was at worst 8:1. A 1-in-256 selector, using seventeen 16-leg structures, is under constuction. The structure described here is in a sense the complement of the laddic,2in that the drive and hold windings are always applied in fixed positions and different functions are generated by linking different sets of output legs.

Two techniques are described for designing multiapertured magnetic structures capable of realizing any specific logic function. The structures are made from rectangular hysteresis loop material. The designs are derived from the corresponding relay contact network by replacing each current carrying conductor in the relay circuit with its analog in the magnetic circuit, a flux-carrying conductor, replacing the emf with a pulsed mmf; and replacing each back contact with a saturable portion of the magnetic circuit in the topological equivalent of the contact network. A flux reversal through a saturated portion may then be blocked by means of an inhibiting Current applied to a suitable winding, the current representing a logical input variable. Thus flux may be ``steered'' through the magnetic circuit in a manner analogous to the steering of current through the contact network. For planar structures the first technique may be used to obtain the analog of series-parallel and bridge type circuits; parallel circuits. It is pointed out that the analog of a relay tree can be used as a standard structure suitable for realizing any Boolean function. Representative examples of both designs are shown, and experimental data are given.