Redcom Laboratories, Inc.

Stromberg-carlson Corporation

Redeom Laboratories, Inc.

Bruce G Littlefield

Charles J Breidenstein

Jerome S Caplan

Charles A Barbe

A TDM switching system for providing selected connections between large numbers of lines and trunks and which may combine, in an integrated system, several TDM switching systems which are adapted to handle smaller numbers of lines and trunks so as to expand the capacity of such smaller TDM systems. The system has a distributed, modular architecture in which the lines and trunks are arranged in a plurality of domains. The domains each have a link controller which links the domains to interdomain PCM highways. The domains each include, as the members thereof, a plurality of devices. These member devices can be port interfaces which connect telephone lines and trunks and convert the analog telephony signals into PCM signals and vice versa, circuits which provide services, telephony processors which contain the data base of the addresses (telephone numbers) of the various lines and trunks, ringing generators, and interface devices which provide a gateway for signals into the domains for the smaller TDM switching systems. Each domain has its own intradomain PCM highway to which the devices are connected and device control links connecting the devices to a link controller and carrying signalling messages. Each domain may have a different complement of devices. Control signals control the telephony signal process along separate links, unique to each device, which connect that device to the link controller.

Time division multiplex (TDM) switching system especially for pulse code

Ring trip is detected when a telephone set which is being rung goes off-hook, through the use of a comparator in which the ringing signal superimposed on battery feed voltage is compared with a fixed reference voltage closer to ground than the battery feed voltage. Inasmuch as the duty cycle of the ringing signal with respect to the reference voltage is less than or equal to 50% under pre-trip (on-hook) conditions and will increase under trip (off-hook) conditions, the comparator output is a square wave form of corresponding duty cycle. An up-down counter is caused to count up when the comparator output wave form is of one level and down when the comparator output wave form is of another level during each cycle of the ringing signal. The counter counts up during the portion of the comparator wave form which determines the duty cycle and down during the rest of the period of the cycle. Underflow and lack of underflow states of the counter respectively indicate nonring trip and ring trip conditions. Logic responsive to these conditions causes deactuation of a ringing relay to enable disconnection of the ringing signal from the ring lead going from the line circuit to the telephone set. The line circuit has a calling bridge which provides an output which is used to prevent the ringing relay from reoperating unless the telephone set remains on-hook after ring trip detection.

Ring trip detection system

High density component mounting back panel for electronic equipment

Synchronous operation of any number of digital switching units of a TDM system is maintained by interconnecting the switching units to a timing signal highway which distributes timing signals generated by sources of such signals in any one of the units. The units are connected successively in a chain by timing signal distribution control lines. Validity signals are generated and transmitted by circuits in each unit along the lines so as to provide for transmission of timing signals generated in the first switching unit on to the timing signal highway and switch over of the timing signal generating function to successive ones of the units when the timing signal generation in preceding units becomes faulty.

Timing signal generation and distribution system for TDM

In a digital data transmission system including one or more matrix switches in which data in digital form is stored in a send memory during one selected time slot of a recurring time frame, transferred to a receive memory and sent out from the receive memory during another time slot of the recurring time frame to establish desired data paths through the switch between selected inputs and outputs, means is provided in the form of a programmable read only memory to control the insertion loss of each data path in a selective manner.

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Honeoye Falls, NY, United States of America

Bruce G Littlefield