GB2086186A

GB2086186A - Telephone answering machine interface

Info

Publication number: GB2086186A
Application number: GB8032247A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1980-10-07
Filing date: 1980-10-07
Publication date: 1982-05-06
Also published as: GB2086186B

Abstract

A telephone answering facility is provided by a fairly simple unit couplable to an existing telephone set and to a cassette tape recorder with a closed loop of tape to provide a prerecorded announcement. An incoming call to a line when the subscriber is away seizes an interface unit when the latter detects ringing. This ringing is rectified (C1-R1-D1-D2) to give DC, which is amplified by a transistor amplifier (T1-T2) to operate an electro-magnetic relay (R1). This closes one contact to loop the line, thus responding to the call, and closes another contact to signal (via EF) to the recorder which thereon starts to send its pre-recorded message (via CD) to the caller. No provision is made for the caller to send a message as this device is intended solely to tell a caller that the wanted subscriber is unavailable. <IMAGE>

Description

SPECIFICATION Telephone answering machine interface This invention relates to a telephone answering machine interface arrangement.

Telephone answering machines as currently used in offices and the like are complex and expensive machines, and the need has arisen for an arrangement to provide the answering facility which is simple and relatively cheap. Such a device would be of use for domestic installation where the user is away for a relatively short period and is not likely to receive many incoming calls during such a short period.

An object of the invention is to provide a simple and inexpensive interface to meet the above need.

According to the invention there is provided a telephone answering machine interface, which when in use is connected to a telephone subscriber's instrument and to a separate cassette recorder, which interface when in use is connected across the line incoming to a said instrument, in which the interface includes means responsive to the reception of a ringing signal and to the persistance of that signal for a preset period to render the connection of the interface to the line effective, and in which when said connection is rendered effective a source of a pre-recorded announcement is connected to the line, for transmission of a pre-recorded message to the caller.

Embodiments of the invention will now be described with reference to the accompanying drawings, in which Fig. 1 is a simplified block schematic to explain the basic principle of the invention, and Figs. 2 and 3 are circuit diagrams of two embodiments of the invention.

Fig. 1 shows how an interface 1 embodying the invention is used in conjunction with an existing telephone 2 and a domestic cassette recorder. The interface can be powered from the telephone (if the subscriber's premises are not too far from the exchange), the mains at the subscriber's premises, or an internal source such as a battery. As will be seen later, the interface 2 contains ail of the circuitry needed to detected an unanswered call, automatically activate the recorder 3, engage the telephone line, and send any pre-recorded signals on the cassette tape to the caller so that the caller can send a message to the interface, e.g.

his own number. The interface then automatically disengages the line and switches off the recorder.

In a preferred form the cassette recorder for an endless loop cassette to which the user can record a message.

We now consider Fig. 2, which is a circuit of an interface embodying the invention, which has a pair of terminals A, B connected to the line to the exchange in parallel with the subset, e.g. through a plug and socket connection in the line's terminal box. When a phone call is initiated, relatively large AC ringing signals are sent down the line to operate the ringer in the telephone set. These AC signals pass via the transformer to Cl-Ri,and thereafter are rectified by D1--D2, to produce a DC signal level across C2. The time constant of R2-C3 is such as to give a gradually increasing direct voltage across C3.

When the voltage across C3 reaches a preset threshold, T1 turns on, followed by T2 via R4. This operates the relay RL, which short-circuits R5-C5, which engages the line so that the caller can receive an announcement. The operation of the relay also starts the motor of an external cassette recorder via the terminals EF, which are the external microphone terminals of the recorder.

The recorder output is then fed to the line via terminals CD. An LED D3 is lit while the relay is operated to indicate that an announcement is in progress.

The sudden decrease in the collector voltage of T2 when it turns on feeds a strong bias back to T1 via R4-C6, and as C6 discharges the bias on T1 weakens until tri turns off, followed by T2. Hence the relay releases. The time constant of C6-R2 is adjusted to give an on period for satisfactory transmission of the announcement. An endlessloop cassette is used so that the tape returns to the beginning of the announcement after the specified on period. In fact, the loop is slightly shorter than this so that at least one complete message cycle is sent. Note that this device merely gives the caller an announcement, but does not allow him time to himself send a message.

The circuit of Fig. 3, on which component values are indicated, is in most respects similar in operation to Fig. 2, but modified to be more suitable for use in conjunction with the British telephone system.

An automatic level control circuit is included, connected from the input from the cassette, to reduce the recorded message to about 1/3 volt for transmission down the telephone line. The speech from the cassette is applied via an amplifier Al to the base of the transistor T4 from which it reaches the transformer. There is a feedback path from the emitter of T4 via another amplifier A2 to the base of transistor T5 to effect this level control.

In this circuit transistor T3 turns on a second relay, which seizes the line as soon as a recorded signal on the cassette activates the level control circuit. If a message is recorded at too low a level, T3 remains off and the line is not seized. However, if the level is too high, the level control circuit levels it down to the correct amplitude. Note that in Fig. 3 the functions performed by one relay in Fig. 2 are split between two relays.

The transformer used in Fig. 3 can be a 1:4 ratio transformer with a split bobbin to ensure that if mains voltages appear across the secondary, the primary voltage is still less than 100 volts. This would need an extra contact on relay 1 , which is open unless ringing signals are on the line. Hence transistor T4 is protected from the very high ringing voltage, approximately 400 volts, which appear on the secondary winding.

1. A telephone answering machine interface,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Telephone answering machine interface This invention relates to a telephone answering machine interface arrangement. Telephone answering machines as currently used in offices and the like are complex and expensive machines, and the need has arisen for an arrangement to provide the answering facility which is simple and relatively cheap. Such a device would be of use for domestic installation where the user is away for a relatively short period and is not likely to receive many incoming calls during such a short period. An object of the invention is to provide a simple and inexpensive interface to meet the above need. According to the invention there is provided a telephone answering machine interface, which when in use is connected to a telephone subscriber's instrument and to a separate cassette recorder, which interface when in use is connected across the line incoming to a said instrument, in which the interface includes means responsive to the reception of a ringing signal and to the persistance of that signal for a preset period to render the connection of the interface to the line effective, and in which when said connection is rendered effective a source of a pre-recorded announcement is connected to the line, for transmission of a pre-recorded message to the caller. Embodiments of the invention will now be described with reference to the accompanying drawings, in which Fig. 1 is a simplified block schematic to explain the basic principle of the invention, and Figs. 2 and 3 are circuit diagrams of two embodiments of the invention. Fig. 1 shows how an interface 1 embodying the invention is used in conjunction with an existing telephone 2 and a domestic cassette recorder. The interface can be powered from the telephone (if the subscriber's premises are not too far from the exchange), the mains at the subscriber's premises, or an internal source such as a battery. As will be seen later, the interface 2 contains ail of the circuitry needed to detected an unanswered call, automatically activate the recorder 3, engage the telephone line, and send any pre-recorded signals on the cassette tape to the caller so that the caller can send a message to the interface, e.g. his own number. The interface then automatically disengages the line and switches off the recorder. In a preferred form the cassette recorder for an endless loop cassette to which the user can record a message. We now consider Fig. 2, which is a circuit of an interface embodying the invention, which has a pair of terminals A, B connected to the line to the exchange in parallel with the subset, e.g. through a plug and socket connection in the line's terminal box. When a phone call is initiated, relatively large AC ringing signals are sent down the line to operate the ringer in the telephone set. These AC signals pass via the transformer to Cl-Ri,and thereafter are rectified by D1--D2, to produce a DC signal level across C2. The time constant of R2-C3 is such as to give a gradually increasing direct voltage across C3. When the voltage across C3 reaches a preset threshold, T1 turns on, followed by T2 via R4. This operates the relay RL, which short-circuits R5-C5, which engages the line so that the caller can receive an announcement. The operation of the relay also starts the motor of an external cassette recorder via the terminals EF, which are the external microphone terminals of the recorder. The recorder output is then fed to the line via terminals CD. An LED D3 is lit while the relay is operated to indicate that an announcement is in progress. The sudden decrease in the collector voltage of T2 when it turns on feeds a strong bias back to T1 via R4-C6, and as C6 discharges the bias on T1 weakens until tri turns off, followed by T2. Hence the relay releases. The time constant of C6-R2 is adjusted to give an on period for satisfactory transmission of the announcement. An endlessloop cassette is used so that the tape returns to the beginning of the announcement after the specified on period. In fact, the loop is slightly shorter than this so that at least one complete message cycle is sent. Note that this device merely gives the caller an announcement, but does not allow him time to himself send a message. The circuit of Fig. 3, on which component values are indicated, is in most respects similar in operation to Fig. 2, but modified to be more suitable for use in conjunction with the British telephone system. An automatic level control circuit is included, connected from the input from the cassette, to reduce the recorded message to about 1/3 volt for transmission down the telephone line. The speech from the cassette is applied via an amplifier Al to the base of the transistor T4 from which it reaches the transformer. There is a feedback path from the emitter of T4 via another amplifier A2 to the base of transistor T5 to effect this level control. In this circuit transistor T3 turns on a second relay, which seizes the line as soon as a recorded signal on the cassette activates the level control circuit. If a message is recorded at too low a level, T3 remains off and the line is not seized. However, if the level is too high, the level control circuit levels it down to the correct amplitude. Note that in Fig. 3 the functions performed by one relay in Fig. 2 are split between two relays. The transformer used in Fig. 3 can be a 1:4 ratio transformer with a split bobbin to ensure that if mains voltages appear across the secondary, the primary voltage is still less than 100 volts. This would need an extra contact on relay 1 , which is open unless ringing signals are on the line. Hence transistor T4 is protected from the very high ringing voltage, approximately 400 volts, which appear on the secondary winding. CLAIMS

1. A telephone answering machine interface, which when in use is connected to a telephone subscriber's instrument and to a separate cassette recorder, which interface when in use is connected across the line incoming to a said instrument, in which the interface includes means responsive to the reception of a ringing signal and to the persistance of that signal for a preset period to render the connection of the interface to the line effective and in which when said connection is rendered effective, a source of a pre-recorded announcement is connected to the line, for transmission of a pre-recorded message to the caller.

2. An interface as claimed in claim 1, and in which the means responsive to the ringing signal includes a rectifier circuit which derives from said signal a direct current, and a relay to which such direct current is applied, contacts controlled by the relay rendering said connection effective and connecting said source of a recorded announcement to the line.

3. An interface as claimed in claim 1 or 2, and in which the source of a recorded announcement is a cassette recorder with a closed loop of tape bearing the recorded announcement.

4. An interface as claimed in claim 3, and which includes a level adjustment circuit adapted to limit the amplitude of the recorded announcement to a value suitable for propagating over the telephone line.

5. A telephone answering machine interface substantially as described with reference to Figs. 1 and 2, or Figs. 1 and 3, of the accompanying drawings.

New claims or amendments to claims filed on 29 Sept. 1981.

New or amended claims:

6. A telephone answering machine interface, which when in use is connected to a telephone subscriber's instrument and to a separate cassette recorder, which interface when in use is connected across the line incoming to a said instrument, in which the interface includes a rectifier circuit which derives from the alternating current ringing signal a direct current which is applied to a delay circuit including a capacitor, in which the capacitor is charged by said direct current at a rate such that its charge reaches a preset level after a preset period, in which when the charge on the capacitor reaches said preset level a relay is operated to render the connection of the interface to the line effective, and in which when said connection is rendered effective a source of a pre-recorded announcement is connected to the line for transmission of that announcement to the caller.