A personal alarm apparatus comprises a wrist mounted R.F. transmitter including a push button trigger and a relay station connected to the telephone line. The relay station on receipt of the transmitted alarm signal dials the first of up to four stored telephone numbers and repeats a digitized vocal...http://www.google.com.au/patents/US4510350?utm_source=gb-gplus-sharePatent US4510350 - Personal alarm apparatus including wrist supported transmitter and receiver/telephone interface circuit
