Doppler type blood flow monitor - acoustic warning can be switched to either output to indicate change in blood flow

摘要

A doppler type blood monitoring instrument with a pair of summing devices (5, 6) and demodulators (9, 10) for the phase shifted signals, passing two output signals D1, D2) to two pulse shapers (14, 15), one connected to two flip-flops (16, 17) interconnected with two AND gates (18, 19) which pass comparison signals to an operational amplifier and a device (23) indicating blood changes, includes an acoustic warning device which also indicates such changes. This device is a loudspeaker (13) which may be used to indicate a change in one direction only, or alternatively, in two directions and is operated by an oscillator (28), and by means of a switch (24) can be connected to either output (D3 or D4).