# US 4,394,775 A · Frequency division communication system wherein conventional transmitter-transceiver can be used as a repeater or local base station

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- Number: US 4,394,775 A
- Document ID: US4394775A
- Status: Granted
- Kind: A
- Application number: 06/266,575
- Filed: 1981-05-22
- Granted: 1983-07-19
- Earliest claimed: 1980-05-29
- Assignees: U.S. Philips Corporation
- Inventors: John Bruinsma
- Web page: https://patentgrep.com/patent/US4394775A

## CPC

- H04B 7/2621: {using frequency division multiple access [FDMA] (H04B7/2615 takes precedence)}
- H04B 1/50: using different frequencies for the two directions of communication
- H04B: TRANSMISSION

## Abstract

Frequency division communication system wherein conventional transmitter-transceiver can be used as or repeater or local base station. No additional transmitter and receiver are required to adapt transceiver to function as interchannel repeater.

## Claims

### Claim 1

A transceiver for use in a frequency division, two-frequency multi-channel communication system having a multi-channel transmitter with transmission channel selection means for selecting a channel transmitter frequency and a multi-channel receiver with receive channel selection means for selecting a channel receiving frequency band, characterized in that said receiver further comprises an automatic control system coupled to said transmission channel selection means and said receive channel selection means, said automatic control system comprising:
a multi-stable periodic switching device for switching the receive channel selection means so as to sequentially select a first channel receiving frequency band and a second channel receiving frequency band, and for switching the transmission channel selection means so as to select a first channel transmitter frequency and a second channel transmitter frequency, said multi-stable periodic switching device having a control input which, in response to a keying signal, arrests the periodic switching therof;
detection means fed by signals received within the frequenccy band of a selected receive channel which, in response to detection thereby of a received signal having predetermined characteristics, applies said keying signal to the control input of said multi-stable periodic switching device and causes said transmitter to transmit information carried by the received signal; and
a steering circuit, coupled between said multi-stable periodic switching device and said transmission channel selection means, having steering modes for determining which channel transmitter frequency is to be selected, in which a first steering mode causes said transmission channel selection means to select said second channel transmitter frequency in response to a received signal within said first channel receiving frequency band and, alternately, to select said first channel transmitter frequency in response to a received signal within said second channel receiving frequency band.

### Claim 2 (depends on 1)

A transceiver as claimed in claim 1 wherein the said detection means produces said keying signal in response to detection of a carrier, modulated or unmodulated.

### Claim 3 (depends on 1)

A transceiver as claimed in claim 1 which further comprising an identification information recognition means responsive to predetermined identification information carried by a received signal, which recognition means inhibits the arrest of said multi-stable periodic switching device and the excitation of the transmitter in the absence of such identification information.

### Claim 4 (depends on 1)

A transceiver as claimed in claim 1 wherein said steering circuit has in addition to said first steering mode, a second steering mode in which said transmission channel selection means is switched to said first channel transmitter frequency in response to a received signal within said first channel receiving frequency band and is alternatively switched to said first channel transmitter frequency in response to a received signal within said second channel receiving frequency band, the transceiver additionally comprising an identification information recognition means responsive to predetermined identification information carried by a received signal, said steering circuit being controlled by said recognition means in such a manner that it operates in the first steering mode in response to a received signal carrying such predetermined identification information and in the second steering mode in response to a received signal without such predetermined identification information.

### Claim 5 (depends on 1, 2, 3, 4)

A transceiver as claimed in claim 1, 2, 3 or 4 which further comprises:
a further control system including manually operable channel selection switches for manually selecting a channel transmitter frequency and a channel receiving frequency band; and a transceiver mode selection switch for rendering said automatic control system inoperative while said further control system is operative and vice-versa.