An experimental switching device is described that has thefollowing properties: (a) sealed metallic contacts, (b) control times in themicrosecond range, (c) coincident selection, (d) memory without holding power and (e) small size. The device, named theferreed, may beused as a crosspoint in telephone switching networks of the space-separation type. The development oj the ferreed is traced from a conceptual model, through realization oj a practical model, to possible applications in switching networks. Two methods of coincident control are discussed, and three devices related to the conceptual jerreed are described briefly.

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An experimental high‐speed signaling system capable of signaling at the rate of 100 decimal digits per second over a variety of existing Bell System transmission facilities is described. This system uses several frequencies in combinations as its code elements. Because the manner of discriminating between different frequencies is significantly different from present‐day practice, the system has been called polytonic to distinguish it from existing multifrequency systems. Signal separation in this system depends not on the steady‐state response of filters, but on the transient response of simple reactive networks. Discrimination is enhanced by the use of rather precise timing in the signal generating mechanism and somewhat less precise timing in the receiver. A second system, capable of signaling at the rate of 300 decimal digits per second over a more restricted range of transmission facilities, is also briefly discussed.

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