Electronic headset telephone

An electronic, line-powered telephone set for use with a telephone headset apparatus having a receiver and a microphone, said telephone set compatible with a standard telephone transmission system having at least first and second lines for establishing a loop connection between said telephone set and a central switching station, said telephone set comprising:

• ringing means, selectively coupled either to said first and second lines or to said first line and a third line, responsive to the presence of an alternating-current ringing signal thereon for heralding an incoming telephone call;
• dialing means for initiating outgoing telephone calls, said dialing means selectably capable of initiating the issuance of dialing pulses and dialing tones on said first and second lines, said dialing means further having memory means for storing dialing sequences and having the capability to issue said stored dialing sequences to said first and second lines under direction of a user;
• rectifying means coupled to said first and second lines for receiving therefrom direct-current supplied from batteries in the central station, and producing a rectified, direct-current signal for powering electronic components of the telephone;
• surge protector means coupled to said first and second lines for preventing internal components of the telephone from being exposed to voltages exceeding a predetermined threshold;
• an electronic hook-switch circuit receiving the rectified, direct-current power signal from said rectifying means, the hook-switch circuit for selectively establishing the loop connection with the central station, such that when a loop connection is established, variations in the amount of current conducted in said loop are used to communicate voice information between the telephone set and the central station, said variations in current being superimposed upon the direct-current signal received from said rectifying means, the hook-switch circuit also providing a switched, direct-current output signal which has a non-zero level only when a loop connection is established
• low-current regulator means receiving the rectified DC power signal for providing a low-current output power signal to components of the telephone set during periods when a loop connection is not established;
• high-current regulator means receiving the low-current output power signal from the low current regulator and the switched direct-current signal from the hook-switch circuit, for providing a higher-current output power signal to components of the telephone set during periods when a loop connection is established;
• bell-tap suppression circuit including an opticoupler, coupled to said first, second, and third lines, for preventing said ringing means from responding to voltage transients on said first, second, and third lines which may be generated during pulse dialing;
• an electronic controlling circuit receiving power signals from said low-current regulator and said high current regulator, said controlling circuit having a plurality of input terminals and a plurality of output terminals,
• electrical storage means receiving said low-current output power signal and said high-current output power signal, for storing electrical energy provided therefrom, said stored electrical energy being used by the dialing means, the hook switch circuit, and the controlling circuit during periods when a loop connection is not established;
• voice signal processing means, including a receiver amplifier and a transmitter amplifier, coupled to said first and second lines, for establishing full-duplex voice communication between the telephone and the central station via a loop connection;
• switching means coupled to said headset apparatus and to the voice signal processing means for identifying the type of said headset, and for adjusting the operation of the voice signal processing means according to the type of the headset;
• indicator means for indicating the gain level of the receiver amplifier, for indicating when a loop connection is established, and for indicating the gain level of the transmitter amplifier;
• a first subset of said controlling circuit input terminals coupled to the output terminals of a plurality of user-operated switches, for receiving a plurality of user control signals therefrom;
• a second subset of said controlling circuit input terminals coupled to said dialing means, for receiving a plurality of dialing control signals therefrom;
• a first subset of said controlling circuit output terminals coupled to said voice signal processing means, for issuing a plurality of volume control signals thereto, the gain of said receiver amplifier being adjusted in response to said volume control signals, and said volume control signals being issued in response to said user control signals;
• a second subset of said controlling circuit output terminals coupled to the electronic hook-switch circuit, for issuing hook-switch control signals thereto, said electronic hook-switch circuit selectively establishing a loop connection with said first and second lines in response to said hook-switch control signals, said hook-switch control signals being issued in response to said dialing control signals and said user control signals;
• a third subset of said controlling circuit output terminals coupled to the indicator means, for issuing indicator control signals thereto, the indicator means responsive to said indicator control signals to indicate the status of the hook-switch circuit, the gain of the receiver amplifier, and the gain of the transmitter amplifier.