Control circuit for telephone answering device

Claim 2

In a telephone answering device of the type wherein an answering cycle is initiated upon occurrence of a ringing signal on the telephone line, said cycle including the transmission of a prerecorded outgoing message and the subsequent recording of an incoming message, a circuit for initiating said answering cycle comprising: a controlled rectifier, triggering means for initiating conduction of said controlled rectifier in response to occurrence of said ringing signal, loading circuit means including said controlled rectifier for loading said telephone line when said controlled rectifier conducts, semiconductor switch means, turned on by conduction of said controlled rectifier, for connecting power to other components of said telephone answering device, and turn-off means for applying a reverse polarity voltage across said controlled rectifier to terminate conduction thereof at the end of said answering cycle, said terminated conduction unloading said telephone line and causing said semiconductor switch means to disconnect power from said other answering device components.

Claim 3

A circuit according to claim 1 for use in a telephone answering device wherein said answering cycle is timed by a control member on an endless tape loop containing said outgoing message, said turn-off means comprising; a capacitor charged during said answering cycle, discharge means, actuated by said control member when said endless tape reaches a cycle terminating position, for applying the charge on said capacitor across said controlled rectifier in a polarity causing turn-off thereof.

Claim 4

A circuit according to claim 1 wherein said semiconductor switch means comprises a diode in series with a source of power and said controlled rectifier, bias from said telephone line clamping off said diode prior to occurrence of a ringing signal, conduction of said controlled rectifier resulting in conduction of said diode to provide power from said source to said other device components.

Claim 5

A circuit according to claim 1 wherein said semiconductor switch means comprises; a transistor, means connecting the base of said transistor to a non-control element of said controlled rectifier for biasing on said transistor when said controlled rectifier conducts, and means connecting a source of power to said answering device other components via the emitter-collector path of said transistor.

Claim 6

A circuit according to claim 1 wherein said triggering means comprises; a rectifier bridge, said telephone line being connected to the input of said bridge, a triggering capacitor connected to the output of said bridge and charged by the ringing signal rectified by said bridge, and means connecting said triggering capacitor to the control element of said controlled rectifier to initiate conduction thereof when the charge on said triggering capacitor reaches a certain level, dc bias from said telephone line thereafter maintaining conduction of said controlled rectifier.

Claim 7

A circuit according to claim 5 wherein said means connecting comprises; a neon lamp connected to fire when the charge on said triggering capacitor exceeds the firing point of said lamp, and means for applying the firing current of said neon lamp to the control element of said controlled rectifier to initiate conduction thereof.

Claim 8

A circuit according to claim 5 further comprising; means for maintaining conduction of said controlled rectifier during said answering cycle despite absence of dc bias from said telephone line.

Claim 9

A circuit according to claim 5 wherein said loading circuit comprises; a loading element simulating the load characteristics of a telephone series connected with said controlled rectifier across the output of said rectifier bridge.

Claim 10

In a telephone answering device of the type wherein a prerecorded outgoing message is delivered from one recording medium to the telephone line and an incoming message subsequently is recorded on another medium, said answering device including means establishing the duration of said answering cycle, a circuit for starting and ending said answering cycle comprising: a. a rectifier bridge connected across said telephone line, b. a controlled rectifier, c. triggering means connected to the output of said bridge and to the control element of said controlled rectifier for turning on said controlled rectifier in response to occurrence of a ringing signal on the telephone line, dc bias from said telephone line thereafter maintaining conduction of said controlled rectifier during said answering cycle, d. an inductor effectively connected in series with said controlled rectifier across the output of said bridge to load said telephone line when said controlled rectifier is on, e. a source of power for other components of said answering device, f. a transistor, the base of said transistor being connected to a non-control element of said controlled rectifier to bias on said transistor when said controlled rectifier is on, said source of power being connected to said other components via the emitter-collector path of said transistor, and g. turn-off means for terminating conduction of said controlled rectifier at the end of said answering cycle.

Claim 11

In a telephone answering device of the type wherein a prerecorded outgoing message is delivered from one recording medium to the telephone line and an incoming message subsequently is recorded on another medium, said answering device including means establishing the duration of said answering cycle, a circuit for starting and ending said answering cycle comprising: a. a rectifier bridge connected across said telephone line, b. a controlled rectifier, c. triggering means connected to the output of said bridge and to the control element of said controlled rectifier for turning on said controlled rectifier in response to occurrence of a ringing signal on the telephone line, dc bias from said telephone line thereafter maintaining conduction of said controlled rectifier during said answering cycle, d. an inductor effectively connected in series with said controlled rectifier across the output of said bridge to load said telephone line when said controlled rectifier is on, e. a source of power for other components of said answering device, f. a transistor, the base of said transistor being connected to a non-control element of said controlled rectifier to bias on said transistor when said controlled rectifier is on, said source of power being connected to said other components via the emitter-collector path of said transistor, and g. turn-off means for terminating conduction of said controlled rectifier at the end of said answering cycle.

Claim 12

A circuit according to claim 9 wherein said triggering means comprises; a trigger capacitor connected across the output of said bridge, said trigger capacitor being charged to a first level by the dc bias on said telephone line and charged to a higher level by said ringing signal, and means operatively connected to discharge said trigger capacitor and thereby provide a trigger signal to the control element of said controlled rectifier only when the charge on said trigger capacitor reaches said higher level.

Claim 13

A circuit according to claim 10 wherein the base and another element of said transistor are connected in series between said inductor and said rectifier non-control element, a current path thereby being provided from one output terminal of said rectifier bridge through said inductor, a junction of said transistor, and said controlled rectifier to the other output terminal of said rectifier bridge, said source of power also being connected to said transistor other element.

Claim 14

A circuit according to claim 11 for use in a telephone answering device wherein said other medium comprises a magnetic tape, the end of said tape having a control element, said circuit further comprising; means for preventing said transistor from connecting said source of power to said other components upon detection of said control element, thereby inhibiting operation of said telephone answering device when insufficient magnetic tape remains for recording additional incoming messages.