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Browse Prior Art Database

Analog Fan In Fan Out for Modems in Multipoint Network Configuration

IP.com Disclosure Number: IPCOM000089515D
Original Publication Date: 1977-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Melanger, J: AUTHOR

Abstract

Shown in the figure is an analog fan-in/fan-out feature which enables modems to be arranged in a multipoint network configuration without using multipoint channels from common carriers.

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Analog Fan In Fan Out for Modems in Multipoint Network Configuration

Shown in the figure is an analog fan-in/fan-out feature which enables modems to be arranged in a multipoint network configuration without using multipoint channels from common carriers.

The fan-in/fan-out feature comprises fan-in and fan-out devices to be attached to the basic output and input circuits of a modem, respectively, At the transmitting end of the modem, the basic output circuit is connected to N- adjustable gain amplifiers. The output from each of these amplifiers feeds a line transformer which interfaces the transmit (XMIT) line. At the receiving end of the modem, each of the receive (RCV) lines 1-N is connected to a line transformer whose secondary output feeds an amplifier. The outputs of all amplifiers 10, 20 and 30 are connected to the automatic gain control circuit (AGC) of the basic input circuit.

Due to the nature of this peculiar multipoint network, all the inputs of the receiver are connected together. This might result in an unacceptable increase of the signal-to-noise ratio. To face this problem, each input circuit is provided with a squelch circuit which inhibits the other idle inputs when it is receiving line signals. For example, when RCV line 1 is receiving line signals, squelch circuit 11 detects the amplifier 10 output level and inhibits AND gates 22-32. The received signal is fed to the basic input circuit through AND gate 12 and OR gate
40.

The arrangement shown i...