Medium ceramic four-pin socket (B4A)

Ceramic B4A has four pins in a square and an orientation notch. The nominal square pitch is 17.4498 mm; pin diameters range from 4.3434 to 5.1562 mm.

B4A is associated with CV398. No precise introduction date is established here.

Numbering needs care: RCA 715C pins are counted clockwise from the notch, while CV398 uses a different convention. Physically matching positions do not justify transferring an electrode number between types without checking.

A ceramic socket photograph shows a reference bar and locking lever. Inside and outside diameters described for that product concern its body, whereas the drawing's pitch and diameters are male dimensions. These must remain separate.

The square of centres and notch must be compared before assigning pin numbers. Changing the numbering convention does not physically move contacts, but can completely change wiring if another type's pinout is copied.

Insertion-gauge dimensions remain separate from terminal dimensions. The reference bar and lever also describe that particular female product. They are not added to the four electrical connections and do not determine male-pin diameter.