https://norbain.com/2-button-3000-series-digital-audiophone-with-electronic-call-tone-videx-0220720-1
Videx 2 Button 3000 Series Digital Audiophone with Electronic Call Tone
The 3171 digital audiophone incorporates a 3 level call tone switch, lock release button and spare service button. For use on the VX2200 digital system....
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https://www.videx.co.uk/catalogsearch/result/index/?p=2&q=video+3001+audiophone+2+button+call+type
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