Browse Prior Art Database

Modem Sharing With Operator Device Unit

IP.com Disclosure Number: IPCOM000042520D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Cukier, M: AUTHOR [+2]

Abstract

Multimodem rack mounting is widely used for important communication networks. Under these circumstances, redundant and costly duplication of operator panels and keyboards can be avoided. A single operator device unit (ODU) may, in other words, be used which would be made to serially communicate with all the rack modems. The ODU is connected to share a modem with its associated Data Terminal Equipment (DTE). For that purpose an interface unit is used for connecting both the ODU and DTE to the same modem while enabling non-disruptive DTE operation. Roughly, the system may be considered as one stealing half a channel for the ODU. The interface circuit is essentially as shown in the figure. STACK A can be seen as a N x 1 RAM (random-access memory).

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Modem Sharing With Operator Device Unit

Multimodem rack mounting is widely used for important communication networks. Under these circumstances, redundant and costly duplication of operator panels and keyboards can be avoided. A single operator device unit (ODU) may, in other words, be used which would be made to serially communicate with all the rack modems. The ODU is connected to share a modem with its associated Data Terminal Equipment (DTE). For that purpose an interface unit is used for connecting both the ODU and DTE to the same modem while enabling non-disruptive DTE operation. Roughly, the system may be considered as one stealing half a channel for the ODU. The interface circuit is essentially as shown in the figure. STACK A can be seen as a N x 1 RAM (random-access memory). When it is written, the address counter is incremented; when it is read, the address counter is decremented. At power-on time, the address counter is cleared. The DTE writes at address zero, and the modem reads at the same address. There is no delay between the DTE and modem. Now, suppose the ODU wants to insert a message of n bits. The following process occurs: Step 1: The ODU sends a SDLC (synchronous data link control)-like message to the concerned modem. This message is stored in STACK B. Step 2: The modem waits for a FLAG occurrence in the data stream coming from the DTE. Step 3: The STACK B contents are copied into STACK A; the address counter value goes from 0 to n. Step 4: Th...