Roy P Sallen

56614608, Aug 26, 1997

Dec 12, 1995

8/570866

Roy Sallen - Wayland MA
Walter James Budzyna - Whitinsville MA
Charles E. Sawabini - Carlisle MA
Drew E. Sunstein - Hollis NH

Secure Technologies, Inc. - Boston MA

G08B 2100

340573

A system has a plurality of transceiver units, including a parent unit and one or more portable and wearable child units, for generating an alarm when a child transceiver unit is more than a predetermined distance away from a parent transceiver unit. The distance is determined by the difference in the phase of a reference signal from the time it is transmitted on an rf signal by a parent unit, received and retransmitted by a child unit, and then received again by the parent unit.

55898211, Dec 31, 1996

Dec 13, 1994

8/355041

Roy Sallen - Wayland MA
W. James Budzyna - Whitinsville MA
Charles E. Sawabini - Carlisle MA

Secure Technologies, Inc. - Boston MA

G08B 2100

340573

A system generates an alarm at one unit of the system when a second unit of the system is more than a predetermined distance from the first unit. The system has a first transceiver unit with a first transmitter for transmitting a first reference signal having a phase with respect to a reference source, and a first receiver for detecting a second reference signal having a phase which bears a relationship to that of the first reference signal. There is a second, portable, transceiver unit with a second transmitter for transmitting the second reference signal after receipt of the first reference signal. The first transceiver unit includes a distance resolver for determining the distance between the two transceiver units from the phases of the first and second reference signals, and an alarm, responsive to the distance resolver, for generating an alarm signal if the distance between the two transceiver units is more than a predetermined amount.