Dial Tone - Variants

Variants

Second dial tone

Private or internal PBX or key phone systems also have their own dial tone, sometimes the same as the external PSTN one, and sometimes different to remind users to dial a prefix for—or select in another way—an outside telephone line.

Secondary dial tone

A secondary dial tone, or second dial tone, is a dial tone-like sound presented to the caller after a call has already been set up. Secondary dial tones are often used in call queuing and call forwarding systems.

Unlike a normal dial tone, a secondary dial tone is provided when a connection has already been established and, except for free calls, is being charged for. Systems using secondary dialtone have been criticized for misleading callers into thinking that they are not yet being charged.

Stutter dial tone

A "stuttered" or interrupted dial tone is often used to indicate that voice mail is waiting (see Message Waiting Indicator), or that a calling feature such as call forwarding has been activated.