GB1488435A - Multi-line multi-mode modulator - Google Patents

Abstract

1488435 Multi frequency data transmission INTERNATIONAL BUSINESS MACHINES CORP 21 Aug 1975 [21 Nov 1974] 30552/76 Divided out of 1488433 Heading H4P The description of the embodiments is identical to the parent Specification, but the claims are directed to a multi line multi mode modulator for successively modulating a plurality of different input signals on to a plurality of output lines in which one of n different modulations of m types can be selected for any output line by having a number of stored addresses at least equal to the number of lines which uniquely define the modulation type for any particular line. Frequency and phase modulation arrangements of the types claimed in Specifications 1,488,433 and 1,488,434 are employed. In the multitone generator per se pairs of frequencies are transmitted to convey information as in "touch tone" signalling, e.g. auto dialling, by selecting one each from two groups A, B each having four frequencies i.e. 16 possible pairs which may provide 10 numeric and 6 control digits. Four parallel data bits D0-D3 identifying pairs of frequencies are applied with anti phase clock pulses C1, C2 to address generator 31-2 which selects increments of angular position ##1 or ##2, D0, D1 selecting one of four values ##1, and D2, D3 selecting one of four values ##2 in C1, C2 clock times respectively, under the control of word LCW. Outputs of 33-2 are applied to one input of 34-2 continually operated in an add mode which acts in conjunction in C1 time with feedback register 36-2 so that ##1 is successively added to its content, and alternately in C2 time ##2 is successively added to content of 37-2, both under control of read/write memory 35-2. After each addition, output is applied through #/sin # converter (ROM table) to a further adder 47-1 and register 45-1, controlled to read during C 1 time and during C2 to write into adder 47-1, output being gated, at trailing edge of C2 to d/a converter 43-2 connected to RC filter 44-2. If the arrangement employs sufficiently low baud rates, band width reduction techniques of copending applications need not be used. Fig. 8 (not shown) discloses a block diagram for multi mode multi line modulators, having m input lines, time showing the modulator which has separate multitone/frequency/phase address generators sequentially enabled in any specified order or any mix of the lines, signals being distributed by a synchronized second multiplexer (63) through m output lines having RC filters (64-1). A common master clock and m address LCW unit defines the modulation required for each line at any one time and which can be changed manually or by programme. Fig. 8 is described in greater detail with respect to Fig. 10 (not shown).