Abstract: To allow PBX or key telephone systems, which are connected to dial pulse central offices, to use discount rate long distance, remote banking, and other services that require DTMF dialing, the system CO interfaces are equipped with a DTMF generator for tone dialing and a loop control relay for pulse dialing, which are under the system control. The user initiates dialing which is in pulse mode by default. After completing the dialing sequence into the CO, by pressing a designated button all other numbers dialed will be in DTMF. After the user hangs up the process may be repeated again. This feature can also be provided in conjunction with auto dialing.

Abstract: A tone source is located at each telephone set of a private branch exchange (PBX) or a key telephone system. The tone source provides call progress tones and warble ring tone, as well as a feedback tone in response to the depression of telephone set keypad buttons by the user. The signaling to the central system unit is transmitted via a digital link.