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HALF-DUPLEX PCM SPEAKERPHONE FOR A DIGITAL TELEPHONE

IP.com Disclosure Number: IPCOM000005557D
Original Publication Date: 1985-Oct-01
Included in the Prior Art Database: 2001-Oct-15
Document File: 2 page(s) / 76K

Publishing Venue

Motorola

Related People

David E. Bush: AUTHOR

Abstract

An alternative solution to the half-duplex speakerphone function in a digital telephone can be accomplished with entirely digital techniques, replacing numerous analog components necessary in the conventional approach.

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MOTOROLA Technical Developments Volume 5 October 1985

HALF-DUPLEX PCM SPEAKERPHONE FOR A DIGITAL TELEPHONE

by David E. Bush

An alternative solution to the half-duplex speakerphone function in a digital telephone can be accomplished with entirely digital techniques, replacing numerous analog components necessary in the conventional approach.

   A typical digital telephone architecture is shown in Figure 1. The unique feature of a digital telephone is that the 64 Kbps PCM encoded voice data is transmitted between the digital switch and the digital telset. The major advantage of this is consistant voice quality since no degradation of the voice signal is possible while it is in a digital form. Another benefit is that by increasing the data rate beyond 64 Kbps, simultaneous data transfers may occur for data processing and signalling purposes.

   Since the PCM encoded voice data are available in the digital telset. the speakerphone function may now take place while the voice is still in digital form. This is shown in Figure 2 where the half-duplex PCM speaker- phone is inserted between the transceiver and the codeclfilter.

   PCM data received from the linecard are demodulated by the transceiver before being clocked into the half- duplex PCM speakerphone circuit. Likewise, transmit PCM data from the codecMilter are clocked into the speaker- phone circuit. The speakerphone circuit simultaneously processes both the transmit and receive data to determine which side of the con...