Abstract:
The use of a group of relays, all having only make contacts interconnected in a manner to allow a single current pulse to selectively operate one relay while at the same time releasing all the other relays, has resulted in the design of circuits where a one-hot out-of-n code can be used to control the operational states of the circuits. The fact that the relays have remanent reed sealed contacts and are thus self-latching greatly simplifies minimumization of peripheral equipment and reduces control complexity since a single current pulse can both select the desired circuit state by operating one of the relays and release any other operated relay.
Abstract:
A single and double wire switching arrangement in which each balanced two-wire transmission circuit is transformer coupled with two single-wire network terminations with capacitive DC isolation between the transformer windings and a reference potential connected between the isolating capacitors. Either of two unbalanced single-wire paths or one balanced two-wire path can be established through the network from each transmission circuit. A single-wire path is sufficient for most functions; however, the two-wire path is available for those functions requiring a metallic or a balanced path. Network blocking is low since the majority of network paths are single wire thus freeing unused single-wire links, for other paths. Supervision can be maintained either at a transmission circuit or at a junctor circuit included in the network path.
Abstract:
An arrangement is disclosed for delaying the release of a dialing connection between a calling telephone station and a central office register when the station prematurely disconnects to permit the station to originate another call within a specified interval of time. The register is returned to a state in which it can accept a new complement of dialing signals. If another call is not originated within the specified interval of time, the register and the dialing connection through the switching network of the central office are released.
Abstract:
There is disclosed a line circuit for use in the path between a switching machine and a telephone station for controlling communication services such as ringing and hold to the station. The line circuit is connected across the communication conduction pairs in a manner which allows removal without interrupting active telephone service. The transient signals which are generated whenever the station makes a transition from on-hook to off-hook and from off-hook to on-hook are used to obviate the need for line current detection. In this manner, the line relay is removed from the series path between the switching machine and the telephone station.
Abstract:
There is disclosed a line circuit for use in the path between a switching machine and a telephone station for controlling the hold function. The hold control circuit is arranged to respond to a momentary transient signal on the communication leads from the telephone station and to the presence or absence of a signal on the A lead from the station for establishing either the hold state or the disconnect state of the line circuit. Structure is disclosed for timing the release of the hold function on communication lead open conditions with the time delay dependent upon the insertion of a diode in series with the timing capacitor to adjust the voltage across the capacitor.
Abstract:
In lossless or low loss conferencing systems it is customary to use a hybrid to convert each station from 2-wire to 4-wire operation. Because of impedance mismatch conditions, reflections can occur at the hybrid interface thereby causing echo and ''''singing'''' problems. Self-cancellation of the reflected signals can be achieved by reversing the phase of the reflected signals through the hybrids and assigning the reversed phase hybrids only to stations connected to the system by trunks. For those stations connected to the system by lines, 5dB pads are used in conjunction with unreversed phase hybrids. In this way complex switching is avoided.