Abstract: An acoustic transducer for producing highly directional characteristics comprises a metalized backplate (130) facing the flat surface (134) of an electrostatically charged electret foil (132). The thickness of the electret foil varies along the length thereof according to a predetermined relationship. The sensitivity of the electret transducer varies directly with the thickness of the electret foil.

Abstract: A rough surfaced backplate has deposited thereon a metallic electrode having a plurality of large areas interconnected by thin strips. The large areas are symmetrically located on opposite sides of the center of the metallic electrode. Furthermore, the distances between the areas is nonlinear. Superimposed on the metallic electrode is an electret foil having a uniform electrostatic charge deposited on the polymer surface thereof.

Abstract: A directional electret transducer comprises an electret foil and a metalized backplate the effective air gap thickness therebetween varying according to a predetermined relationship. The sensitivity of the electret transducer is directly proportional to the effective air gap thickness. The effective air gap thickness is realized in three ways: first, a plurality of equal diameter holes are drilled to varying depths in the aforesaid backplate; second, a plurality of holes of varying diameters are drilled through the aforesaid backplate; third, a plurality of equal diameter holes are drilled through the aforesaid backplate, the density of the holes varying. In each of the aforesaid three ways, the variation is according to the predetermined relationship.

Abstract: Highly directional response patterns can be obtained by connecting microphones or loudspeakers with tubular coupling path structures. The coupling paths comprise a plurality of elements (110,111 . . . 157) arranged in pairs (110,111; 112,113; . . . 156,157) so that for every element (110) below a center line (102) there is an element (111) above the line. Furthermore, the relationship between the element pairs is nonlinear. The desired directional response comprises one main lobe and a plurality of substantially smaller lobes below a determinable threshold value. The elements may be a bundle of tubes (90) or a plurality of apertures (110,111, . . . 157) in a single tube (100).

Abstract: The disclosure shows a telephone range extender which is automatically adaptable to the length of the connected subscriber loop. A loop resistance detector within the range extender discriminates between loops within a plurality of ranges of lengths. For extremely short loops not requiring range extension, the range extender circuits are disconnected from the loop. For intermediate length loops, the gain of a bidirectional voice frequency amplifier is set at a low value to provide just sufficient gain for these loops. For longer loops, the gain of the amplifier is increased to provide sufficient amplification for the longer range. For extremely long loops, the range extender is disconnected since such loops must be served by remote amplification facilities. An automatic range extender of this type is shown connected behind the first stage of the central office switch in order to concentrate range extenders on a larger plurality of subscriber loops.

Abstract: A directional array of acoustic transducers is disclosed. The acoustic transducers are arranged colinearly and in pairs symmetrically about a center line of the directional array. The distances of the acoustic transducers on either side of the center line of the array are neither linear nor monotonic. These distances are calculated using a recursive far field response formula which effectively reduces sidelobe magnitudes to a desired design amplitude envelope. The response produced is highly directional, comprising one main lobe and a plurality of sidelobes each less than the desired design envelope, which is substantially lower than the main lobe but of arbitrary (e.g., stepped) shape.

Abstract: A simple and inexpensive direct current voltage level detector is shown which has a significant immunity against interfering alternating current signal components. The output of a standard analog threshold detector is successively sampled by clock pulses having twice the repetition rate of the frequency of the expected interfering alternating current components. By requiring two successive samples to be above the threshold of detection, immunity is provided against false detection due to temporarily exceeding the threshold level due solely to the positive excursion of the interfering alternating current components. Simple clock-driven flip-flops are used for the sampling and a simple logical AND gate is used to detect the successive samples.

Abstract: An electrical protector device (10) for grounding excessive voltage and excessive current to safeguard telecommunications circuits includes a heat coil assembly (100) for sensing and directing excessive current to ground, and a spark gap arrester (200), axially aligned with the heat coil assembly (100), for sensing and controlling excessive voltage. Whenever an overcurrent condition is encountered, heat coil mechanism (110) is displaced to provide metallic contact of the incoming line to a ground structure (300). In addition, the device is adapted to provide protected testing of both incoming pairs and office equipment. Two test points (123) formed as part of the heat coil assembly (100) are in contact with the individual wires of the incoming line. These two test points are accessible through apertures (402) in the protector housing (400).

Abstract: Portable test apparatus utilized to access a field of test points comprises either a single access tool (100) or a multiple access adaptor (200) depending on the mode of testing required. Tool (100) is usually employed for accessing the field to effect a periodic testing whereas adaptor (200) is generally used for planned test activities. Tool (100) comprises body (111), guide assembly (150) and cover plater (170) which house clamp assembly (130) and pin contact assembly (180). Clamp assembly (130) operates in scissor-like fashion for engaging and disengaging tool (100) from test field grips (401). Spring-loaded pins (181) penetrate apertures (403) within the test field to contact the test points. Adaptor (200) comprises body (211), center panel (240) and guide (260) which enclose pin contact assembly (280); in addition, cam-lever drive assembly (210) attached to body (211). Drive assembly (210) has means for grasping a frame (50) associated with the test field so as to draw body (211) towards frame (50).

Abstract: The disclosure shows a telephone range extender which is automatically adaptable to the length of the connected subscriber loop. A loop resistance detector within the range extender discriminates between loops within a plurality of ranges of lengths. For extremely short loops not requiring range extension, the range extender circuits are disconnected from the loop. For intermediate length loops, the gain of a bidirectional voice frequency amplifier is set at a low value to provide just sufficient gain for these loops. For longer loops, the gain of the amplifier is increased to provide sufficient amplification for the longer range. For extremely long loops, the range extender is disconnected since such loops must be served by remote amplification facilities. An automatic range extender of this type is shown connected behind the first stage of the central office switch in order to concentrate range extenders on a large plurality of subscriber loops.

Abstract: DC-to-DC converter circuitry which provides input-to-output isolation, sensing of load conditions and minimal standby losses comprises: a blocking oscillator including switch means (10) and energy storage means (50); and control circuitry (12,32,46,47) for sensing load demands and reducing the oscillator frequency under no-load conditions.

Abstract: The disclosure shows a telephone range extender which is automatically adaptable to the length of the connected subscriber loop. A loop resistance detector within the range extender discriminates between loops within a plurality of ranges of lengths. For extremely short loops not requiring range extension, the range extender circuits are disconnected from the loop. For intermediate length loops, the gain of a bidirectional voice frequency amplifier is set at a low value to provide just sufficient gain for these loops. For longer loops, the gain of the amplifier is increased to provide sufficient amplification for the longer range. For extremely long loops, the range extender is disconnected since such loops must be served by remote amplification facilities. An automatic range extender of this type is shown connected behind the first stage of the central office switch in order to concentrate range extenders on a larger plurality of subscriber loops.

Abstract: The disclosure shows a telephone range extender which is automatically adaptable to the length of the connected subscriber loop. A loop resistance detector within the range extender discriminates between loops within a plurality of ranges of lengths. For extremely short loops not requiring range extension, the range extender circuits are disconnected from the loop. For intermediate length loops, the gain of a bidirectional voice frequency amplifier is set at a low value to provide just sufficient gain for these loops. For longer loops, the gain of the amplifier is increased to provide sufficient amplification for the longer range. For extremely long loops, the range extender is disconnected since such loops must be served by remote amplification facilities. An automatic range extender of this type is shown connected behind the first stage of the central office switch in order to concentrate range extenders on a larger plurality of subscriber loops.

Abstract: Multipair cable testing apparatus for detecting transpositions and reversals in the cable pairs includes master unit (100) located at one end of the cable and remote unit (200) located at the other end.Master unit (100) comprises: pair address generator (120) for automatically and sequentially stepping through a grouping of pairs simultaneously terminated by master unit (100); sequencer (110) to sequentially connect, during each testing step, a pair under test to voltage measurement means (150) and then to resistance measurement means (160); indicator means (170) to display the results of the two measurements; and communicating means (175) to transmit the terminal address of the pair under test to remote unit (200).

Abstract: A subscriber loop carrier system is shown in which coin first and dial tone first pay stations can be serviced through the carrier system without modifying the central office. Coin supervisory states are detected at the central office terminal of the system, translated into unique cyclic codes for transmission through the system and detected at the remote terminal by reapplication of the coin supervisory states at the remote terminal. Coin first and dial tone first modes of operation are accommodated with simple option plugs.

Abstract: An electrical terminating arrangement (100) serving as an interconnection juncture for joining central office equipment with outside plant facilities, an access point for testing and a protection provisioning point comprises connector apparatus (402), tie cabling (500) and protector apparatus (110) wherein the conventional stand-alone test field appearance is eliminated. Test access is provided directly through sockets (130) in front face (113) of protector apparatus (110), or indirectly to test lands through apertures (403) in protector device (400) inserted in sockets (130). Reliability is achieved by utilizing connector (170) to couple protector apparatus (110) to a mated connector on the outside plant stub cable. Installation complexity is reduced by employing snap-in details (190) as well as plug-in details.

Abstract: An automatic equalizer for digital transmission systems is disclosed including a variable gain amplifier in one branch of a two-branch admittance circuit. The branch including the amplifier includes two frequency-dependent admittances while the other branch is insensitive to frequency. Varying the gain of the amplifier provides a minimum phase network which can be automatically adjusted to compensate for varying lengths and gauges of telephone pairs. This configuration permits digital transmission in the subscriber loop plant at rates up to 200 kilobits per second.

Abstract: A digital transmission system is disclosed in which time slots in selected frames are reserved for supervisory signaling bits. These signaling bits can be used to represent a large number of supervisory states by assigning at least three bit patterns to each of two interleaved streams of supervisory bits. These bit patterns may include, for example, continuous ones, continuous zeros and alternating ones and zeros. A supervisory state encoder and decoder for these bit patterns are disclosed.

Abstract: A testing system is disclosed for telephone subscriber loops which are in part derived by multiplex facilities in what have come to be known as pair gain systems. In this testing arrangement, the local drop wires from the remote terminal of the pair gain system to the subscriber are separated from the carrier system itself and tested by connecting them to a separate metallic pair extending from the central office to the remote terminal location. Simultaneously, the carrier-derived portion of the subscriber loop is connected to automatic testing apparatus which sequences through a plurality of automatic tests for not only transmission characteristics of the carrier-derived channel but also tests for the ability of the derived channel to transmit supervisory information such as ringing, coin control and party identification information. The remote terminal of the pair gain channel is selectively terminated by a reflective or absorptive termination to assist in these testing procedures.

Abstract: A ring-trip detection circuit is disclosed which is suitable for use at the remote terminal of a pair gain system, i.e., a system designed to supply more than one telephone subscriber with loop service over a single pair of metallic wires. The ring-trip detector circuit comprises a simple filter and semiconductor threshold circuit which responds to subscriber loop currents to disable ringing signals when the subscriber goes off-hook. The detector circuits are powered entirely by the ringing signal itself and thus draw no power when in the inactive state and require no auxiliary powering source in the active state.