512E Electronic Call Tone. The Videx 512 extension sounder is used to extend the sound of the call received on the handset. . Wall mountable plastic enclosure. Dimensions: 110mm (L) x 70mm (W) x 30mm (D). 512R requires 12V ac input and is suitable for telephones with ac buzzers. 512E generates its own tone and requires a 12V ac or dc signal