In order to achieve true "hold button" activation, we created a small module called a TEMHA (telephone extension hold music activator). This line powered activator tells the OHP 4500 or OHP 5500 unit when the phone is on-hold. Only phone extensions with a TEHMA can put a call on-hold with music using the phone's hold button.   Availability: Usually ships in 2-3 business days. Telephone Extension Hold Music Activator 7000P4$25.95     This product backed by a "no questions asked" 30-Day Money Back Guarantee