Each fuse featured a protruding sharp-pointed pin which thrust outward when electrical overloads or transient power spikes caused them to blow. The crewmember who found a blown fuse had to pull the bad one and replace it with a good one, of appropriate voltage and amperage rating.
Locating the blown fuse was not always easy. Fuse panels, especially in the DSO's rear cockpit station, lined the left and right side panels. There were hundreds of fuses, each about the size of a Zippo cigarette lighter. Sometimes more than one fuse might be blown, but in the subdued light they were hard to locate.
The recommended procedure for locating the blown fuses called for wiping the hand across the power panels to feel the sharp extruding pins. So it was not surprising that DSO's wryly described the practice as one of first feeling the panels and then counting the blood streaks on their hand to learn how many fuses were blown.
Those protruding pins weren't really that sharp, but sometimes had a rough burr or jagged edge that could hurt a hand wiping very hard across the power panels. More than one DSO has come away with a scratch or two on his hand. During preflight checks it was standard operating procedure to check every power panel for blown fuses before electrical power systems were activated. Visual scanning of the power panels with a flashlight was not as quick or effective as wiping the hand over the panels.
In time, as we flew the planes over a span of several years, the supply of spare fuses dwindled. Or perhaps spares from one plane were borrowed for another. Anyway, there were blank or empty slots where spare fuses used to be. So finding the right voltage/amperage replacements for blown fuses became more difficult.
That Mach 2 delta-winged wonder was, in many ways, very "high tech" for its day. But in one feature it was anything but high tech. We actually had a clothesline-type rope and pulley system running from the pilot's front cockpit to the DSO's aft one, passing along the middle station of the navigator on the way. A small bag or pouch attached to the line could carry written messages from one crewmember to another. The system was useful on those rare occasions when the intercom failed, but it was installed for another purpose entirely.
Back in those dark cold war era times, when it was possible that bomber crews could be sent to deliver nuclear weapons upon the "evil empire", procedures were formal and strict about proper verification of "GO CODES". It was necessary for at least two crewmembers to independently de-code radio received GO CODES which might send us off to war. The decoded messages, and related items, could be physically exchanged between crew members only by such a mechanism. There was no station-to-station movement possible for people in that tight, cramped fuselage. Only a small bag, attached to a clothesline, could maneuver the narrow passage fore and aft.
Ah yes, those days of yore. Funny what one remembers, isn't it? And no, we didn't have two tin cans and a string as a back-up intercom. Hmmmm. Now that's an idea.