TO-71 Metal Can
Transistor Can Packages TO-71 Case style, Multi-pin Metal Can
TO-71 Package Layout and Schematic
The TO-71 package is a through-hole component.
The metal can may be used to attach a heat sink. However all the leads are electrically isolated from the case, and both sections are electrically isolated from one another.
The graphic shows dual N-Channel Field Effect Transistors [FET].
FETs using this package type include; 2N5545, 2N5546, and 2N5547
The TO-71 only defines the physical size, the FET pin out is just one possible example.
Note the pin locations vs the location of the metal tab, for a 6-pin metal can.
Sockets are available to mount an 8 pin TO-71 IC device [or 6-pin].
PCB conversion boards may be purchased for adapting an 8-pin DIP to a TO-71 package, or circular TO-71 to 8-pin DIP Adapter. A similar package is the TO-78 Case or TO-77 package.
Note that even though the TO-71 case has been deactivate, it does not mean that the case will not be found as an option for a part. Primarily being deactivate means that new components will not use this package style or size. However components designed into the TO-71 package before the case went obsolete could still be produced in this case style.