Trunk Type Research Articles

D4 Digital Channel Bank Family: The Channel Bank

The D4 channel bank is the most recent Western Electric product in an evolution of time-division multiplex terminals for digital transmission facilities. D4 incorporates many technical innovations relative to the earlier developed D1D, D2, and D3 channel banks but is fully compatible with these earlier banks. D4 banks may be operated in any of five different modes as required to connect to a particular digital carrier facility (T1, T1C, T2, or FT2). The D4 channel bank is partitioned into common equipment and channel units. The common equipment provides digital line interface, pulse code modulation coding and multiplexing, alarms, trunk processing power, power fusing, and distribution. Individual channel units provide the circuits that interface to external circuits. There are many different versions of channel units including standard interoffice voice-frequency trunk types and those supplying data and special services.

Strip detection using relaxation

This note describes some experiments in the detection of parallel sided strips using a relaxation-like process which iteratively reinforces collinear or anti-parallel edges. The process was tested on two types of data, tree trunks and runways.

A case of giant pigmented nevus : bathing trunk type

A case of giant pigmented nevus : bathing trunk type

The E6 Negative Impedance Repeater

The E6 repeater is a low-cost, transistorized, voice-frequency, two-way repeater for use in the exchange area plant, including use in trunks between local offices and between local and toll offices. It permits both types of trunks to be operated at low net loss, while meeting the impedance requirements placed on trunks between local and toll offices. These features are possible because of a unique method of repeater design, in which the impedance-matching function and the gain function are allocated to separate portions of the repeater and are separately adjustable. The impedance-matching function is accomplished by means of a line building-out network, which permits any cable pair associated with the repeater to be built out and made to match the impedance of the toll office. The gain unit presents the same image impedance, which is essentially independent of gain adjustment. Changes in gain are controlled by two resistive, adjustable artworks — one in the series-connected negative impedance converter, and the other in the shunt-connected converter. In previous designs of negative impedance repeaters, complex impedance networks were required for adjustment of both gain and impedance match. The E6 repeater also incorporates novel mechanical features, with transistorization resulting in low power drain and less heat dissipation in the telephone central office. Power is derived from the existing 48-volt central office battery.

Classification et repartition verticale des pecopteridees dans le bassin houiller du nord de la France

Abstract The history of the definition and classification of the genus Pecopteris is reviewed, and the vertical distribution of species in the Carboniferous coal basin of northern France is summarized. Data on the different types of trunk and their relations with the fruits are included.

Mechanism of Metallic Friction

DR. BOWDEN and his collaborators1 in their investigations on the mechanism of metallic friction need have little doubt that, under many of the conditions of load and speed used in practice, the local temperatures reach a high value. Very high local temperatures are attained in very short intervals of time, as those who have observed 'seizure' taking place between the cylinder or liner and piston in an internal combustion engine can testify. The opportunity of witnessing this occurrence is rare in modern engine design with closed crank cases, but in the days of the horizontal gas engine, with the open-ended cylinder and trunk type piston, high temperature, often a white heat, was frequently observed when 'seizure' took place.