My mums dog a little shitzue is driving her mad with barking all the time, she has brought a collar that gives off a high pitch sound when he barkes, but it is not working, just scaring mums other dog,

she would like to get a different sort of collar to sort this out, can anyone recommend one please,

the dog is very bad and things are reaching a pitch, so I thought i would ask the forum for help???

Em