The use of distinctive ring signals has long been known. For instance, when multi-party lines were in vogue, telephone central offices would place a distinctive ring signal on the multi-party telephone line to notify one of the parties that it was his/her telephone that was being signalled. Telephone central offices today offer a distinctive ring feature which enables multiple devices connected to a single telephone line to distinguish which of the devices is being accessed. For instance, if a telephone and a facsimile are connected to the same line, the facsimile can be programmed to respond to a particular ring cadence.
U.S. Pat. No. 5,086,458 to Bowen describes the provision of a plug-in, tone responsive unit at each telephone extension. A central answering unit responds to a caller-initiated, telephone company-generated ring signal and establishes a connection with the calling phone. Each remote unit responds to a different predetermined tone frequency. When the caller pushes a key on a touch-tone phone key pad, the responding remote unit generates a ring signal for that extension.
U.S. Pat. No. 5,142,569 to Peters et al. describes a device which prevents a subscriber receiver from receiving ring signals other than those having a prescribed ring cadence. U.S. Pat. No. 5,323,451 to Yatsunami describes a facsimile which is programmable to respond to a distinctive ring pattern from a central office.
When multiple telephones are present in an open work area, it is sometimes difficult to distinguish which telephone is ringing. Moreover, when plural telephones, ring at the same time, it can become even more difficult to determine which telephones are to be answered. While it is known that a private branch exchange (PBX) can provide distinctive ring signals to individual telephone extensions, many PBX facilities do not have such capability and those which do generally provide only a limited number of distinctive ring cadences, (e.g., one indicating that the call is from an internal extension, and another indicating that the call is from an outside line).
Accordingly, it is an object of this invention to provide a distinctive ring annunciator which is directly connectable to a telephone line outlet.
It is another object of this invention to provide a distinctive ring annunciator which is both directly connectable to a phone outlet and is programmable to enable a user to determine the precise ring or other annunciation that is to occur upon receipt of a telephone ring signal.