Ran into an odd one yesterday. Customer had an Axxess system upgraded to a 5000. They have and existing Valcom single door phone controller hook to a co position. The new system would recognize the ringing unless I had my butt set connected in parallel.
Went back today and connected a 1muF capacitor in series with a 4K ohm resistor to emulate the additional ren. Likely could have used a higher resistore value but it works without volume issues. FWIW the customer said they only use it for a signal to get up and answer the door when the receptionist is away from her desk.
