Firing Module

Firing Module is the final link which connects the squib to the Phase III System. The squib, of course, is connected to (in contact with) the Pyrotechnic Device to be ignited under control of the Phase III System.

The firing module is a small aluminum box which houses various electronic components. Basically the firing module takes input control signals and outputs firing power to the desired squib. The firing module is intended to be near the devices to be fired and thus has various output termination options. Output termination options means the various ways in which the squib may be connected to the firing module, or thus terminated. (Note: squib may mean more than 1 squib per circuit)

Each type of firing module is electrically identical and only varies physically to accommodate different ways in which to connect the squib. Firing modules are therefore completely interchangeable anywhere within the physical layout.

Since the firing modules are electrically identical and interchangeable, the question then is how are the modules distinguished from one another? This is accomplished by a double hex rotary thumbwheel address switch on each module. The thumbwheel switch is externally accessible and a firing module address may be selected in a matter of seconds. This means that any firing module may be positioned anywhere within the physical layout and then simply set to the correct address.

Each type firing module has 16 firing circuits. The module type (output termination options) dictates the manner in which the squib is connected to each of the 16 circuits. Each and every squib therefore has a specific module address and a shot address, or the location of a particular squib on that particular module. This address / shot code is the information which the computer uses to talk to a specific squib. Up to 128 module addresses times 16 shots per module gives up to 2048 individually addressable firing circuits.

For safety and operational purposes the firing module also has a toggle switch. This is a 2 position switch, being either shunted or armed (unshunted). In the shunted position all firing power outputs are disconnected and all 16 squib connectors (output termination options) are individually short circuited together (shunted). The module electronics, however, are still operative and the entire system may be powered up for check out in complete safety and in a non fire condition with all squibs shunted. Successful operation and communication within the entire layout of the system at this point (shunted) indicates that all is OK and it is safe to proceed.

The firing modules also have provisions for sending squib continuity information back to the computer. With the shunts opened the entire layout may then be checked to insure all the squibs are connected and ready to fire.