Radio telephone signaling: Low-frequency system

A signaling system is described which serves to extend to the field of radio telephony the same sort of calling facilities as are now available in wire telephony. By its means the radio attendants or subscribers are enabled to signal each other without requiring that the called party should have to listen with a receiver. The system is intercommunicating with a capacity for a large number of stations on one wave length. It has a range of operation extending as far as a radio channel suitable for the commercial transmission of speech can be reliably maintained, and offers a very satisfactory degree of freedom from interference. Furthermore, it employs simple, standard types of telephone apparatus. Some possible fields of usefulness of the system, its outstanding characteristics, and the apparatus which it employs are described.