Abstract: This tone detector which is suited for dual tone multifrequency (DTMF) digit detection, separates the pairs of tones into a low frequency and high frequency group in which the other frequency group is attenuated by filtering. The amplitude of the low and high frequency groups serve as separate variable threshold reference signals. Individual tones are bandpass filtered with their corresponding outputs converted into an amplitude signal. The amplitude of the individually bandpass filtered tone signals are compared against the corresponding low or high frequency variable threshold signal for a determination of whether a tone is present. Preferably, additional validation steps are applied to the preliminary tone decisions to provide improved digit detection accuracy, especially in the presence of other signals such as speech.

Abstract: A transmission scheme serially propagates time slot data to a plurality of TSI modules with time slot data contained in one TSI frame being serially transmitted from module to module in a daisy-chain technique. A dedicated outbound transmission bus transmits the frame of data from one module to a dedicated inbound transmission bus of another module. The outbound and inbound data buses are connected by separate buses on a backplane which is coupled to each of the TSI modules. Preferably, the TSI modules do not transmit selected ones of the stored data to end destinations until the last TSI module has received the frame of data so that all modules can begin the transmission in time synchronization. Maximum transfer data rates can be achieved since undesired transmission line characteristics or disruptions are minimized by the use of dedicated input and output transfer buses between the modules.

Abstract: An arrangement where a plurality of digital signal processors cooperate in the performance of a digital signal processing function. The processors are interconnected by means of a synchronous network which provides time division multiplexed communication links between processors for communicating intermediate processing results therebetween. The synchronous network includes a plurality of port circuits each associated with one of the processors. The network generates timing signals defining frames of time slots and defining superframes comprising N frames. Each port circuit can control the transmission of digital data from a memory of its associated processor during M1 time slots of each superframe. Each port circuit can also control the writing of digital data to its associated processor during M2 time slots of each superframe. The value of N, the number of frames per superframe, is programmable. The values of M1 and M2 are also programmable for each port circuit.

Abstract: A method and apparatus for generating accurate digital representations of one or more sine waves. A digital signal processor is used to generate the sample digital values, spaced at period T, of a sine wave of frequency F, F<1/2T, using recursive methods. The magnitude of the generated sample values is stabilized and controlled by normalizing the recursively generated samples from time to time, but not necessarily after each recursive calculation. Methods are described for generating values based on the values of two previously generated samples using the recursion formula: y(n)=y(n-1)2 cos.omega.-y(n-2) where .omega.=2.pi.FT and y(n), y(n-1) and y(n-2) represent three consecutive sample values. The normalizing factor, used for multiplying a recursively generated sample value to stabilize the amplitude, associated with this calculation is ##EQU1## where A is the desired amplitude.

Abstract: An arrangement for selectively connecting a first or a second frequency synchronous timing signal to an outgoing conductor is disclosed. When a transition from the first to the second timing signal occurs, the first timing signal is inhibited from being transmitting on the outgoing conductor and the logical AND of the second timing signal and a delayed version of the second timing signal is transmitted on the outgoing conductor for approximately one period of the timing signals. Thereafter, the second clock signal is transmitted on the outgoing conductor. Arrangements are also disclosed for switching from the second timing signal to the first timing signal.

Abstract: A dual tone multifrequency and dial pulse receiver that receives 8000 digital data words per second, each of the data words including eight PCM bits representing the analog signal transmitted from a subscriber set and also including a line status bit indicating the DC status of the line. The receiver includes a time-shared processor which processes the PCM bits of 4000 words per second to detect tone-pairs and which also processes the line status bit of 4000 words per second to detect valid dial pulse sequences. The time-shared processor stores one of a first plurality of code words in a register when a tone-pair is detected and stores one of a second plurality of code words in the register when a valid dial pulse sequence is detected. Advantageously, the receiver can detect either dual tone multifrequency or dial pulse signaling from a subscriber even though the type of signaling to be used by the subscriber is not known a priori.

Abstract: A digital concentrator system for use with a plurality of digital carrier systems in the telephone subscriber loop plant is disclosed. The concentrator system comprises a central office terminal (100), a remote terminal (102), and an interconnecting digital carrier path (108). In the transmit direction at each terminal (110,112), a plurality of multiplexed encoded signal streams are demultiplexed and the encoded signals stored. A selected number of encoded signals are retrieved and multiplexed for transmission to a distant terminal (112,110) as a concentrated pulse stream (123,175). In the receive direction at each terminal (110,112), the encoded signals in the multiplexed concentrated stream (125,177) are demultiplexed and stored. The stored encoded signals are retrieved and the original number of encoded signal streams are derived for transmission to the carrier terminal (100,102).

Abstract: A digital concentrator system for use with a plurality of digital carrier systems in the telephone subscriber loop plant is disclosed. The concentrator system comprises a central office terminal (100), a remote terminal (102), and an interconnecting digital carrier path (108). In the transmit direction at each terminal (110,112), a plurality of multiplexed encoded signal streams are demultiplexed and the encoded signals stored. A selected number of encoded signals are retrieved and multiplexed for transmission to a distant terminal (112,110) as a concentrated pulse stream (123,175). In the receive direction at each terminal (110,112), the encoded signals in the multiplexed concentrated stream (125,177) are demultiplexed and stored. The stored encoded signals are retrieved and the original number of encoded signal streams derived for transmission to the carrier terminal (100,102).

Abstract: A digital concentrator system for use with a plurality of digital carrier systems in the telephone subscriber loop plant is disclosed. The concentrator system comprises a central office terminal (110), a remote terminal (102), and an interconnecting digital carrier path (108). In the transmit direction at each terminal (110,112), a plurality of multiplexed encoded signal streams are demultiplexed and the encoded signals stored. A selected number of encoded signals are retrieved and multiplexed for transmission to a distant terminal (112,110) as a concentrated pulse stream (123,175). In the receive direction at each terminal (110,112), the encoded signals in the multiplexed concentrated stream (125,177) are demultiplexed and stored. The stored encoded signals are retrieved and the original number of encoded signal streams derived for transmission to the carrier terminal (100,102).

Abstract: A digital concentrator system for use with a plurality of digital carrier systems in the telephone subscriber loop plant is disclosed. The concentrator system comprises a central office terminal (100), a remote terminal (102), and an interconnecting digital carrier path (108). In the transmit direction at each terminal (110,112), a plurality of multiplexed encoded signal streams are demultiplexed and the encoded signals stored. A selected number of encoded signals are retrieved and multiplexed for transmission to a distant terminal (112,110) as a concentrated pulse stream (123,175). In the receive direction at each terminal (110,112), the encoded signals in the multiplexed concentrated stream (125,177) are demultiplexed and stored. The stored encoded signals are retrieved and the original number of encoded signal streams derived for transmission to the carrier terminal (100,102).

Abstract: A digital concentrator system for use with a plurality of digital carrier systems in the telephone subscriber loop plant is disclosed. The concentrator system comprises a central office terminal (100), a remote terminal (102), and an interconnecting digital carrier path (108). In the transmit direction at each terminal (110,112), a plurality of multiplexed encoded signal streams are demultiplexed and the encoded signals stored. A selected number of encoded signals are retrieved and multiplexed for transmission to a distant terminal (112,110) as a concentrated pulse stream (123,175). In the receive direction at each terminal (110,112), the encoded signals in the multiplexed concentrated stream (125,177) are demultiplexed and stored. The stored encoded signals are retrieved and the original number of encoded signal streams derived for transmission to the carrier terminal (100,102).