DETAILED DESCRIPTION What is claimed is: 1.
An arrangement for remotely testing, from a test location, the transmission characteristics of modified duobinary regenerative repeaters in situ in a repeatered line, said remote testing arrangement comprising: means for generating a modified duobinary pulse test pattern composed of repetitious patterns of pulses, each said test pattern characterized by the presence of two pulses of one state followed by two pulses of the opposite state, which is followed by two pulses of said one state, said generating means comprising: means to vary the repetition rate of said test patterns, thereby changing the pulse density, and means to invert the polarity of the pulses in the pattern at any one of a number of predetermined rates, thereby generating one of a number of predetermined audio frequencies, one said predetermined audio frequency for each repeater location, said generating means having an output; means for transmitting the predetermined audio frequency from the output of a repeater to said test location, said transmitting means having an output; means for measuring the amplitude of the predetermined audio frequency, said measuring means having an input; and means for selectively and simultaneously connecting the output of said pulse pattern generator to said repeatered line and said transmitting means to the input of said measuring means, and for selectively and simultaneously connecting the output of said pulse pattern generator to the input of said measuring means and disconnecting said transmitting means therefrom.
2.
The arrangement of claim 1 wherein said means for generating further comprises: timing means; counting means having one input connected to the timing means, having a programmable second input so as to obtain a variation in the pattern density as desired, and having a plurality of outputs; dividing means having one input connected to the timing means, having a programmable input so as to obtain specified divisions of the timing frequency, and having an output; inverting means having an input connected to the output of the dividing means, having as a first output the input frequency and as a second output the output of said inverting means; logic means having a plurality of inputs connected to outputs of said counting means, having inputs connected to the outputs of said inverting means, and having an output; and coupling means having an input connected to the output of said logic means and having an output
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I/O Systems 
