Telecommunication system with automatically switched modems

• US 4,013,956 A
• Filed: 05/05/1975
• Issued: 03/22/1977
• Est. Priority Date: 05/09/1974
• Status: Expired due to Term

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Refflinghaus, Bernd, Lahmer, Jurgen, Dornaus, Johannes
• Primary Examiner(s): Safourek, Benedict V.
• Assistant Examiner(s): Ng, Jin F.
• Application Number:
  US05/574,614
• Time in Patent Office: 687 Days
• Field of Search: 325/21, 325/22, 325/9, 325/10, 325/3, 179/2 E, 179/2.5 R, 179/41
• US Class Current: 375/222
• CPC Class Codes: H04M 3/40 Applications of speech amplifiers
• CPC Class Codes: H04Q 3/0016 Arrangements providing connection between exchanges

Abstract

A telecommunication system in which two terminal stations are coupled to one another via a telephone exchange and the transmission paths between the exchange and the terminal stations are provided with pairs of modems for transmitting, via the transmission paths, information signals of modulation types which are different in the terminal stations and in the transmission paths, the modems nearer to the exchange being switched off by means of an auxiliary signal the frequency of which corresponds to a component of the frequency spectrum of the modulation type employed in the transmission path. Thus information transmission in the telephone exchange is obtained in the same modulation type as employed in the transmission paths so that unnecessary conversion from one type of modulation to the other is avoided.

Claims

1. Telecommunication system of the type comprising two terminal stations which are coupled to one another for the transmission of information signals via a transmission path which includes at least one telephone exchange, at least one pair of modems which are included in one of the parts into which the telephone exchange divides the transmission path and serve to convert a given modulation type to a given other modulation type suitable for the part of the transmisson path situated between the said modems and vice versa, the improvement wherein of the pair of modems the one nearer to the exchange includes a signalling receiver means responsive to the detection of a given signalling signal from a terminal station for delivering a start signal at an output, and an auxiliary-signal generator means connected to that output for supplying, under the control of the start signal, an auxiliary signal constituted by at least one frequency component occurring in the frequency spectrum of the said second modulation type to another part of the transmission path, which part is connected to the said telephone exchange, said modem nearer to the telephone exchange including an auxiliary-signal detector means responsive to the detection of the said frequency component in a signal originating via the telephone exchange from another part of the transmission path connected to the telephone exchange for delivering a switching signal, and switching means connected to the auxiliary signal detector and to the auxiliary signal generator for disconnecting said auxiliary signal generator and for shunting this modem under the control of the switching signal.

2. Telecommunicating system as claimed in claim 1, wherein the auxiliary signal is a pilot signal of a given amplitude, and the detector includes a threshold device arranged so that the detector delivers the switching signal when the said received frequency component exceeds the threshold value of the threshold device.

3. Telecommunication system as claimed in claim 1, wherein the auxiliary signal is a frequency from the upper range of the frequency band employed by the said other modulation type.

4. Telecommunicaton system as claimed in claim 1 further comprising a timer coupled to the auxiliary signal generator for switching off the auxiliary-signal generator after a predetermined time after it has been switched on.