Information on this page has been taken from documentation provided on the Internet by Invisible Software. Pointers to the Invisible Software website contributed by Louis Ohland.

The Invisible Network Model 300/A adapter is a part of the complete network system offering of Invisible Software. The system includes the proprietary NET/30 Network Operating System. In addition to it, Invisible Network also runs the IBM PC LAN Program, Novell Netware, Torus Tapestry, CBIS Network-OS, and other IBM NetBIOS-compatible operating systems.

Model 300/A has a 16-bit interface and operates at 3.0 Mbps, 1.8 Mbps, 1.4 Mbps, or 0.7 Mbps. The card contains a custom-designed LAN Controller Chip and uses double twisted pair wiring and telephone type modular jacks.

Before installing the Invisible Network Model 300/A Adapter, you must set the switches and jumpers. The switches and jumpers are used to enable the termination resistors, select the ROM size and set the option jumper.

Note: Never run Automatic System Configuration with Model 300/A. The automatic configuration does not configure the network board correctly. You must manually configure the board as described in the Hardware Installation Manual (see Links below).

Network Operation

The network is wired in daisy chain fashion. This means that the stations are connected to the cable one after the other, with each station connected both to the next station and also to the previous station.

Every station in the network must have an address. Each address is a number ranging from 0 to 63, and no two stations in the network can have the same address. You must select one computer on your network to act as the master station. The master station must have the highest address, and must be the first to be powered on.

The default network speed setting is 3.0 Mbps. All the boards in the network must be set to operate at the same speed. The other speeds are provided for Model 300/A to communicate with older models of Invisible Network that operate at slower speeds.

Note: The speed you select affects the maximum allowed length of the network cable. The maximum cable length should not exceed 800 feet (250 meters) when operating at 3.0 Mbps; 1000 feet (300 meters) at 1.8 Mbps; 2000 feet (600 meters) at 1.4 Mbps; 1300 feet (400 meters) at 0.7 Mbps.

Termination

The termination resistors must be enabled on the two stations at the extreme ends of the daisy chain, and must be disabled at all other stations. The function of the termination resistors is to minimize the reflection of signals inside the network cable.

To enable the termination resistors, set switches SW2-1, SW2-2, SW2-3, and SW2-4 to the ON or CLOSED position. To disable the termination resistors, set switches SW2-1, SW2-2, SW2-3, and SW2-4 to the OFF or OPEN position.

Selecting the ROM Size

The Invisible Network Adapter currently uses a 16K ROM. The ability to use a 32K ROM has been provided to allow for a possible future upgrade.

The ROM size is selected by jumpers W2, W3, and W4. For 16K ROM, default configuration, jumpering is W2(B and C), W3(A and B) and W4(A and B). For 32K ROM, use W2(A and B), W3(B and C) and W4(B and C).

Note: The ROM is included mainly to support diskless workstations. If you are not using a diskless workstation, disable ROM at adapter configuration time. The network runs much faster if you disable the ROM and load the TransBIOS/NetBIOS software into RAM instead. When the ROM is enabled, the Invisible Network claims 32K of memory from DOS. Refer to the NET/30 software manual for a full discussion of network memory usage.

Setting the Option Jumper

Model 300/A has one jumper W1 which currently performs no function. It is provided to allow for possible future upgrades. For jumper W1, place the shorting blocks on posts A and B.