The setup you are describing soubds like a communicall/vision combined warden call/door entry system. Do they still need the warden call facility? To keep the pendants you would need to fit a warden call system which is quite a limited range, tynetech, chubb, tunstall or entrotec had a go but i think they abandoned the project. You may need to leave the tunstall equipment in situ and recable and fit new standalone equipment alongside if you cant source a combined system. Tbh its a steep learning curve and a life critical safety system so if you are not familiar and not looking to move into that market sector i'd leave it or give them a **** off price and subby it if you win.