I was not able to edit my comments regarding the various ringing arrangements, due to this forum's timing rules, so please insert these comments in my above message at the appropriate point.
(2) (a) it is wired as part of a larger wiring scheme, called "common ringing" (the individual ringer is abbreviated CMB for "common bell." In this scheme, the ringing current comes from a local supply of generator, such as a wall-mounted power unit (20- or 30-type) or from a small "wall wart" type supply, the 118A, that mounts inside the KSU. The ringers are factory-wired in series with the network capacitor.
(2) (b) Similar to the above scheme (local generator supply) but the ringers are energized via a diode matrix, allowing the ringers in telephones of a large system to be arranged in groups that may or may not overlap. The network capacitor is bypassed in this scheme, since the ringers are operated with DC via the diodes in the matrix block.
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To wire a key telephone for line ringing, you can either punch down the ringer pair (slate/yellow) of the running cable directly onto the CO T&R terminals in the KSU or at an intermediate wiring block,
**OR**
You can open the telephone, and find the red/black ringer leads that are terminated on terminals RT and RR, (you will also see the slate/yellow pair terminated on those screws) and move them to the T&R of the CO line you want to ring on that telephone. Example 1T & 1R for line 1, 2T & 2R for line 2, etc. Doing it this way, you would wire one telephone for ringing on line 1, and another telephone for ringing in line 2.
