Don't know what part needs repair or who to call?

I have a NuTone Radio Intercom System, Model IMA- 4006 Series, which was installed in 1997. The door speakers,(2) w/Chime Pushbutton), are Models IS-67 & 69 Series. Had problems with static in 1999, then serviced by: IDS Security,Inc, in Roselle, IL. Probable cause for static was said, was the wind from outside on certain days. He fooled with a few wires and it worked for about a year and a 1/2. Now can't get voice to transmit to any of the speakers. All we hear is static no matter how low we turn the sound down. The clock still keeps perfect time. Could this be caused by an old battery or transformer? Please reply. Thank you, Mrs. P.M.C.

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