GB2151881A - Telephone instruments - Google Patents

Abstract

In a loudspeaking telephone instrument a single changeover contact arrangement 5 is used to select either loudspeaking or handset operation while effectively short-circuiting respectively the handset speech circuit 3 or the loudspeaking circuit 4. <IMAGE>

Description

SPECIFICATION Telephone instruments The present invention relates to telephone instruments.

In particular the invention is concerned with telephone instruments having provision for handset and loudspeaking operation.

According to the present invention in a telephone instrument having a first set of speech circuits for loudspeaking operation and a second set of speech circuits for handset operation, each set of speech circuits having first and second terminals and the respective first terminals being arranged to be connected to respective line terminals of the instru ment, there is provided a changeover contact arrangement having its effective moving contact connected in common to the second terminals of the sets of speech circuits and its effective fixed contacts connected to respective first terminals, whereby selectively one or other of said sets of speech circuits is arranged to be connected effectively between said line terminals of the instrument in dependence upon the position of said moving contact while the other of said sets of speech circuits is effectively short circuited.

Telephone instruments in accordance with the present invention will now be described by way of example with reference to the accompanying draw ing, of which Figures 1 and 2 respectively show schematically so called ' two-wire" and "three-wire" systems.

Referring first to Figure 1, in a loudspeaking telephone instrument, indicated as two units 1 and 2, one terminal of a handset speech circuit 3 and one terminal of a loudspeaking speech circuit 4 are connected together and to the moving contact of a set of changeover contacts 5. The other terminal of the loudspeaking speech circuit 4 is connected directly to one line conductor 6 while the other terminal of the handset speech circuit 3 is arranged to be connected by way of hook switch contacts 7 to the other line conductor 8.

In dependence upon the state of the changeover contacts b in operation either the speech circuit 3 or the speech circuit 4 will be short-circuited while the other of these speech circuits will be connected between the conductors 6 and 8.

Referring now to Figure 2, where the same reference numerals are used as far as possible, a bell 9 is housed in or adjacent the unit 1, and a first quench circuit comprising a resistor 10 and back-toback zener diodes 11 is provided in the unit 1. A second quench circuit comprising a resistor 12 and back-to-back zener diodes 13 is provided in the unit 2. The first quench circuit is arranged to be con nected in parallel with the bell 9 by means of additional hook-switch contacts 14, while the second quench circuit is arranged to be connected in circuit by means of changeover contacts 15 operating with the changeover contacts 5.

When the changeover contacts 5 are in the position shown in Figure 2 the loudspeaking speech circuit 4 is short-circuited and the handset speech circuit 3 may be connected to the lines 8 and 6 by way of the hook-switch contacts 7. So long as the handset (not shown) is offhookthe contacts 14 will connect the first quench circuit in parallel with the bell 9.

When the contacts 5 are changed over for loudspeaking operation the handset (not shown) will normally be on-hook and the contacts 14 will be open, but in this condition the contacts 15 will be operated to connect in the second quench circuit.

1. A telephone instrument having a first set of speech circuits for loudspeaking operation and a second set of speech circuits for handset operation, each set of speech circuits having first and second terminals and the respective first terminals being arranged to be connected to respective line terminals of the instrument, wherein there is provided a changeover contact arrangement having its effective moving contact connected in common to the second terminals of the sets of speech circuits and its effective fixed contracts connected to respective first terminals, whereby selectively one or other of said sets of speech circuits is arranged to be connected effectively between said line terminals of the instrument in dependence upon the position of said moving contact while the other of said sets of speech circuits is effectively short circuited.

2. A telephone instrument in accordance with Claim 1 wherein said changeover contact arrangement comprises a single changeover contact set.

3. A telephone instrument substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

4. A telephone instrument substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.

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

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Telephone instruments The present invention relates to telephone instruments. In particular the invention is concerned with telephone instruments having provision for handset and loudspeaking operation. According to the present invention in a telephone instrument having a first set of speech circuits for loudspeaking operation and a second set of speech circuits for handset operation, each set of speech circuits having first and second terminals and the respective first terminals being arranged to be connected to respective line terminals of the instru ment, there is provided a changeover contact arrangement having its effective moving contact connected in common to the second terminals of the sets of speech circuits and its effective fixed contacts connected to respective first terminals, whereby selectively one or other of said sets of speech circuits is arranged to be connected effectively between said line terminals of the instrument in dependence upon the position of said moving contact while the other of said sets of speech circuits is effectively short circuited. Telephone instruments in accordance with the present invention will now be described by way of example with reference to the accompanying draw ing, of which Figures 1 and 2 respectively show schematically so called ' two-wire" and "three-wire" systems. Referring first to Figure 1, in a loudspeaking telephone instrument, indicated as two units 1 and 2, one terminal of a handset speech circuit 3 and one terminal of a loudspeaking speech circuit 4 are connected together and to the moving contact of a set of changeover contacts 5. The other terminal of the loudspeaking speech circuit 4 is connected directly to one line conductor 6 while the other terminal of the handset speech circuit 3 is arranged to be connected by way of hook switch contacts 7 to the other line conductor 8. In dependence upon the state of the changeover contacts b in operation either the speech circuit 3 or the speech circuit 4 will be short-circuited while the other of these speech circuits will be connected between the conductors 6 and 8. Referring now to Figure 2, where the same reference numerals are used as far as possible, a bell 9 is housed in or adjacent the unit 1, and a first quench circuit comprising a resistor 10 and back-toback zener diodes 11 is provided in the unit 1. A second quench circuit comprising a resistor 12 and back-to-back zener diodes 13 is provided in the unit 2. The first quench circuit is arranged to be con nected in parallel with the bell 9 by means of additional hook-switch contacts 14, while the second quench circuit is arranged to be connected in circuit by means of changeover contacts 15 operating with the changeover contacts 5. When the changeover contacts 5 are in the position shown in Figure 2 the loudspeaking speech circuit 4 is short-circuited and the handset speech circuit 3 may be connected to the lines 8 and 6 by way of the hook-switch contacts 7. So long as the handset (not shown) is offhookthe contacts 14 will connect the first quench circuit in parallel with the bell 9. When the contacts 5 are changed over for loudspeaking operation the handset (not shown) will normally be on-hook and the contacts 14 will be open, but in this condition the contacts 15 will be operated to connect in the second quench circuit. CLAIMS

1. A telephone instrument having a first set of speech circuits for loudspeaking operation and a second set of speech circuits for handset operation, each set of speech circuits having first and second terminals and the respective first terminals being arranged to be connected to respective line terminals of the instrument, wherein there is provided a changeover contact arrangement having its effective moving contact connected in common to the second terminals of the sets of speech circuits and its effective fixed contracts connected to respective first terminals, whereby selectively one or other of said sets of speech circuits is arranged to be connected effectively between said line terminals of the instrument in dependence upon the position of said moving contact while the other of said sets of speech circuits is effectively short circuited.

2. A telephone instrument in accordance with Claim 1 wherein said changeover contact arrangement comprises a single changeover contact set.

3. A telephone instrument substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

4. A telephone instrument substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.