Explosive well tool firing head

An explosive well tool firing head comprising:

• a housing tube having a bore therein between a first end and a second end;
• first screw threads at said first end compatible with operating signal attachment means;
• second screw threads proximate of said second end compatible with an explosive well tool means;
• an operating signal contact means within said housing tube bore proximate of said first end for operatively receiving an operating signal;
• detonator retainer means at said second end for securing the position and alignment of an electrically initiated explosive detonator to project axially beyond said second housing end;
• a capacitive firing cartridge within said housing tube bore between said contact means and said detonator retainer means;
• electrical continuity connections between said firing cartridge and said contact means;
• and,
• electrically conductive leads from said firing cartridge to a detonator secured within said retainer means.