Related Clues

• It may follow a click
• Indication of service availability
• Sound after a hang-up
• "It's okay to call now" signal
• Receiver sound
• Signal to place a call
• Caller's need
• Cell phone's lack
• "Ready" signal of a kind
• Landline signal
• Sound from a receiver
• Calling sound
• Phone sound
• Hum on a line
• 'Go ahead and call' sound
• Hum on the line
• Caller's go-ahead
• It's a mix of 350 Hz and 440 Hz in the United States
• Landline sound
• Feature of a landline, but not a cellphone