Urmet video intercom

[Davi.p]

Hi, i wanna to understand this broken video intercom by Urmet, an Italian company, this device communicate video-audio and call signals on only 2 wires that carries also the DC supply of 48v, the part broken is the external calling place with videocam, opening this i see 2 very small components exploded that has the tipical shape and brown color of the ceramic smd caps but i'm not sure them are, one leg of them are connected each one to the 2 contacts for the 2wire comms+psu line, the other one goes to the 2 output pins of a "differential driver" AD8131 (datasheet https://cdn.badcaps-static.com/pdfs/...9c9350ea38.pdf), i'm not expert so i have first tried to change those 2 with 2 similar items took from an old harddisk board, 2 capacitors, but the system doesn't work (the system is made with 3 elements, the "external place", a specific power supply for DIN guide, a receiver/monitor for house, this last two used for tests are new). So i have 2 doubts, 1. there is a npn mid-power after the diode bridge after the 2 wire input contacts (diode bridge because no need to respect polarity in the 2 wire cabling) that "in circuit" measure in diode mode test 0,082 between Emitter-Base, and a near mid power transistor is quite warm.. but this is not the question, THE 2. IS: in the datasheet i've linked there's an example schematic at page 18 that don't have capacitors between input line and AD8131, do you think i have to suppose those 2 was another type of item like a protection? There exists a component type that is made to explode at a certain voltage? Since them are not varistors that usually are grey/black and are connected to gnd, here there is any gnd. Thanks.