Importance

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Abstract

A data link is additionally provided in a digital channel bank type transmission system without displacing or degrading any present voice or signaling channel capacities. The additional data channel is obtained by 'borrowing' a major portion of the signaling subframe channel. A transmit circuit (FIG. 3 and FIG. 8) serves to time division multiplex a data channel into the signaling subframe channel by transmitting the signaling framing pattern in an intermittent periodic manner with preselected data bits interposed therebetween (waveform TDATA of FIG. 5). At the remote receiving terminal, a subframe recovery circuit (FIG. 7) serves to recover the signaling framing pattern embedded in the multiplexed subframe channel. A receive circuit (FIG. 4) at the remote terminal is responsive to a signal from the subframe recovery circuit to separate out the data bits in the multiplexed subframe channel.

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First Claim