Press "6" at the busy signal and hang up. Your phone will ring when the extension if available. Press "6" again to cancel before you get your callback. Isoetec Digital Systems Display/Data Phone Press "Cb." Soft key at the busy signal. Replace the handset or press "HF". Wait for the double tone. When the extension is no longer busy, it will automatically call you back. Isoetec IDS M Series Telephones When you hear the busy signal, press the "CALL BACK" key. Hang up. When you are signaled, lift the handset or press the "HF" key. Press the blinking "CALL BACK" key. PCS Digital Telephone Press "cbck" at the busy signal. When a station is available, pick up the handset. To cancel, press "del". Vodavi StarPlus Phone System Press the pre-programmed CALL BACK button. Hang up. When the busy station becomes available, you will be signaled. See also redial Vertical service code References Calling features