Browse Prior Art Database

Single Cable Communication With Noise Pulses

IP.com Disclosure Number: IPCOM000084126D
Original Publication Date: 1975-Sep-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Owen, CE: AUTHOR

Abstract

A communication system is described, in which a number of stations on a single cable convey service requests and addresses to a controller using a pulse-modulated noise carrier. More than one station may simultaneously request service from the controller in a nonpolling multidrop mode.

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Single Cable Communication With Noise Pulses

A communication system is described, in which a number of stations on a single cable convey service requests and addresses to a controller using a pulse- modulated noise carrier. More than one station may simultaneously request service from the controller in a nonpolling multidrop mode.

In a simple system, having a large number of not very active stations, it is better for the stations to interrupt the controller rather than they be polled in turn. This requires an "OR" of signals as in US Patent 3,818,447.

Referring to section A of the figure a station is addressed by a command using a conventional modulation scheme, and a response using the same modulation is given by the station clocked by reference to an oscillator locked to the command bits from the controller. A gap is left between command and response for an interrupt noise pulse, plus return delay time.

On seeing an interrupt, the controller can send out an interrogate command (see section B of the figure) which causes all interrupting stations to start transmitting their addresses and dropping out in turn, leaving only the highest priority address transmitted to the controller. These address bits are sent as noise pulses at a slower rate than normal to allow each station to read each bit.

A very small chance exists of noise pulses cancelling. This does not matter if each command addressed to station carries a tag to allow response only if the station is interr...