|
US2890311A
|
|
Thermal sensing unit
|
|
US2890297A
|
|
Transducer assembly
|
|
US2922835A
|
|
Electrical security cable
|
|
US2853557A
|
|
Sound distribution system
|
|
US2842623A
|
|
Transistor amplifier for telephone instrument
|
|
US2802904A
|
|
Telephone switch mechanism
|
|
US2886623A
|
|
Battery assembly for hearing aids
|
|
US2717937A
|
|
Fire detector
|
|
US2761918A
|
|
Amplifier with gain control and power control
|
|
US2745508A
|
|
Microphone support
|
|
DE1008356B
|
|
Listener for the hard of hearing
|
|
GB702315A
|
|
Improvements relating to hearing aids
|
|
US2698368A
|
|
Fire alarm
|
|
US2718563A
|
|
Microphone
|
|
US2764640A
|
|
Hearing aid apparatus
|
|
US2611829A
|
|
Audiphone
|
|
US2549259A
|
|
Radio tuner for hearing aid apparatus
|
|
US2469024A
|
|
Fire alarm switch
|
|
US2497336A
|
|
Casing for unitary hearing aids
|
|
US2435302A
|
|
Telephone system having a calling and supervisory signaling device
|
