GB1308162A - Telephone systems - Google Patents

Abstract

1308162 Radio signalling; automatic exchange systems H G LYNFIELD 24 April 1970 19824/70 Headings H4K and H4L. Means are provided whereby a telephone subscriber may communicate with other subscribers over the exchange system by the use of a portable radio transmitting and receiving telephone instrument which may be moved from room to room without the need of a cord connection to the system. A base unit comprising a mainsoperated radio transmitter and receiver is connected via a conventional hybrid network to the telephone line and co-operates with a batteryoperted portable unit, the battery being disconnected when the handset is on the cradle of the portable unit. A different carrier frequency is used for each direction of transmission. When the handset is lifted the carrier wave transmitted is received by the continuously operative base unit receiver to operate a relay which connects the base unit to the telephone line and switches on the base unit transmitter. The dial pulsing contacts in the portable unit break the power to the transmitter in pulses corresponding to the number dialled and the carrier-operated relay at the base station follows these pulses and breaks the telephoneline accordingly to simulate a standard dialling signal. After the dialling has been completed continued reception of the carrier wave at the base unit causes the carrier operated relay to remain closed so that the system is operative for two-way voice communication. Details of the base unit, Fig. 2.-The telephone lines are connected via terminals 58, 60 to a network 62 which converts from a twowire to a four-wire system and provides impedance matching, click suppression and level control. Signals from the portable unit are received via the duplexer 70 by the receiver 68 and the resulting audio signals are supplied via network 62 to the line. A normally open relay 72 is closed in response to a carrier signal received at 68 to energize the transmitter 66. This relay also closes and opens a contact connecting terminals 116, 118 of network 62 via a diode bridge 74 in response to the presence or absence of a carrier from the portable unit. The bridge 74 ensures that the polarity will always be the same across the relay 72 irrespective of the polarity of a given telephone line connection. Incoming audio signals from the line are supplied via network 62 and transformer 84 to the radio transmitter 66 for transmission to the portable unit via duplexer 70, the handset at the portable unit having been lifted in response to a ringer in the base unit.