Abstract: A recording and reproducing machine in which electrical signals are recorded on a recording medium while the medium is driven forwardly along a predetermined path. Recording and reproducing means are switched between record and reproducing modes. Detecting means are associated with means for switching electrical connections in the machine between record and reproducing modes. The detecting means assume a predetermined condition when the end of the last recorded signal on the recording medium is adjacent to the recording and reproducing means. The driving means can then be operated to drive the medium forwardly only if the switching means are in the record mode.

Abstract: A device for use with equipment such as a telephone answering machine whose operation can be controlled by on hook busy signals transmitted to the equipment. Included in the device are switching means which, when actuated, cause transmission of the outgoing signal from the telephone answering machine to be terminated and actuation of a busy signal detector. If an incoming busy signal is present, the detector generates a predetermined output signal which disconnects the telephone answering machine from the phone lines. The switching means may be actuated by sensing means which detect when the amplitude of the outgoing signal falls to a value below a predetermined level and stays at that value for a short time, within a continuing outgoing signal, or for a long time at the end of an outgoing signal. Alternatively, the switching means may be actuated periodically during transmission of an outgoing signal.

Abstract: An apparatus for coupling a machine, such as a telephone answering machine, to a telephone line. Included in the apparatus is an optical isolator having a first semiconductor device which, in use, is connected across the line and emits radiation whose intensity represents the level of direct current flowing through the device. A second semiconductor device receives radiation from the first device and generates a current representing the intensity of the radiation. Initially, the apparatus operates in a voltage monitoring mode, wherein the current through the first device represents the level of direct voltage on the line. The apparatus distinguishes therefore between an incoming ringing signal and an outgoing dialling signal. If an incoming ringing signal is detected and the call is not answered by the subscriber lifting his handset, the apparatus operates to connect an associated telephone answering machine to the line and is then switched to a current monitoring mode.

Abstract: A remotely controllable electrical equipment is fitted with a decoder device associated with which is an unlocking circuit. Access to the electrical equipment is obtained by transmitting an access signal from a remote coder device. The access signal is made up of three groups of pulsed electrical signals, each group comprising two pulses of frequencies different from each other. The first group of pulses unlocks the unlocking circuit for a first predetermined interval of time. If the second group of pulses arrives within this first predetermined interval of time the unlocking circuit is unlocked for a second predetermined interval of time. If the third group of pulses arrives in the second predetermined interval of time an output signal is applied to the associated electrical equipment. Control signals for operating the equipment can then be transmitted from the coder device to the equipment via the decoder device.