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Multiplexing of Pulse Code Modulation and Pulse Frequency Modulation

IP.com Disclosure Number: IPCOM000092748D
Original Publication Date: 1967-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Divine, D: AUTHOR

Abstract

This circuit permits transmission of both high information rate Pulse Code Modulation data and low information rate Pulse Frequency Modulation data. The transmission is effected on light beam channel 8 between gallium arsenide injection laser transmitter 26 and silicon photodiode receiver 28. PCM data involves synchronous transmission or nontransmission of a pulse at prescribed constant intervals. PFM data involves transmission of pulses at asynchronous positions. The circuit delays each PFM pulse that occurs at a PCM time by a fixed amount.

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Multiplexing of Pulse Code Modulation and Pulse Frequency Modulation

This circuit permits transmission of both high information rate Pulse Code Modulation data and low information rate Pulse Frequency Modulation data. The transmission is effected on light beam channel 8 between gallium arsenide injection laser transmitter 26 and silicon photodiode receiver 28. PCM data involves synchronous transmission or nontransmission of a pulse at prescribed constant intervals. PFM data involves transmission of pulses at asynchronous positions. The circuit delays each PFM pulse that occurs at a PCM time by a fixed amount.

PFM pulses are developed by block 10 and PCM clock pulses are developed by block 12. PCM pulses are developed from block 14. There is Anding at And 16 and delaying in delay unit 18 of the PFM and PCM clock pulses. There is inverting of a PCM clock pulse in Inverter 20 and Anding with PFM pulses in And
22. Finally, the delayed PFM pulses and the PCM pulses are passed via Or 24 to transmitter unit 26 which provides modulated output to channel 8.

At receiver 28 a clock 30 is synchronized with the transmission PCM clock
12. By Anding in And 32 the transmitted pulses with the clock 30 pulses, the PCM data pulses are provided. By inverting in Inverter 34 the 30 clock pulses and Anding them in And 36 with the receiver 28 pulses, the PFM data pulses are obtained. This circuit provides high-quality voice transmission, e.g., 10 kilopulse PFM, with a 72 kilobit PCM inf...