Patent ID: 6181916
Filing Date: 2001-01-30
Classification: H04B,H04M

Abstract:
A communication system comprising:a primary unit having a first transmitter for transmitting a first signal at a first instance and a first receiver for receiving a second signal at a second instance, said primary unit being adapted to be energized by a power source having a predetermined voltage level, said primary unit including a mode-changing device coupled to said first transmitter and adapted for monitoring said predetermined voltage level, said mode-changing device generating a mode-changing signal responsive to said predetermined voltage level falling below a specific value, said mode-changing signal being transmitted by said first transmitter at a third instance; and,a secondary unit having a second transmitter for transmitting said second signal at said second instance and a second receiver for receiving said first signal at said first instance and said mode-changing signal at said third instance, said secondary unit having a first communication mode and a second communication mode, said second communication mode being a shutdown mode, said secondary unit including means coupled to said second receiver for changing said secondary unit from said first communication mode to said shutdown mode responsive to said receipt of said mode-changing signal.