Abstract: A microphone holder for surveillance work and adapted to support a microphone in a concealed position when the holder is taped to the upper torso of a surveillance agent and to avoid clothing rustle and bulges resulting from the normal wear of the holder. The holder is of a flexible rubber material capable of moving with the wearer to permit comfortable use and avoid detection by persons under surveillance. The holder has an upper surface of a generally convex shape and a lower surface which is nearly flat but slightly concave. The upper surface is provided with a recess for the retention of a small microphone that can be un-encased and recessed below the upper surface to avoid clothing rustle. Microphone leads are kept below the upper surface in a groove to further avoid a detectable impression through the clothing of a wearer. Recording means which may include transmitting means is typically located elsewhere on the wearer.

Abstract: A multi-drop local area network utilizes alternating current power lines as a transmission channel. Identical transceivers are used as a master and as up to 255 slaves. Each transceiver comprises modulator and demodulator units and a microprocessor control unit which may be connected to a host. The modulator and demodulator are connected to the alternating current power line through a high pass filter comprising a split bobbin, iron core transformer having an air gap which also provides impedance matching. The demodulator includes a clipper and analog circuitry providing a band pass filter and generating a square wave corresponding to the received carrier. A state machine acting as a digital filter produces a received carrier signal only when each half cycle of the carrier square wave is of the proper duration and the carrier signal has existed for slightly more than one half of the transmitted bit duration, which is a predetermined number of carrier cycles.

Abstract: A telephone system having a remote microphone and associated transmitter, and a network located receiver for signals outgoing over the telephone network and including a local loudspeaker to broadcast signals incoming over the telephone network wherein the loudspeaker audio level is controlled to vary with the level of the received microphone signal. The level of the loudspeaker signal is increased when the received microphone signal increases, and vice versa, allowing the user to control the loudspeaker level by adjusting mouth-to-microphone distance or speech loudness. In particular implementation the signal applied to the network from the remote microphone receiver is automatically attenuated above a certain level to match network requirements. The degree of attenuation is used to cause a corresponding increase in the loudspeaker volume level. Harmful feedback is avoided since loop gain remains constant.

Abstract: A portable telephone or other signaling system features a remote or portable unit responsive to operator voice and control signals to modulate infrared emitting diodes with narrowband, FM low duty cycle pulses which are received by a telephone network unit operative to demodulate the infrared signals, control the telephone network connection and to transmit and receive voice signals from the network. The portable unit utilizes narrowband FM pulse modulation to optimize the use of battery power. The portable unit further includes means for transmitting on-and-off hook indicia and dialing pulses with the same efficient, narrowband FM pulse modulation. The network base unit includes infrared receiving and decoding means in order to identify audio signals and apply them to the telephone network as well as to detect dial pulses and on- and off-hook indicia to process them for connecting and disconnecting the network unit to the telephone network.

Abstract: A sensitive radar signal detector is provided which is operative to reliably detect low level radar radiation characteristic of scattered radiation of very short duration and unknown frequency. Received radar signals which are mixed with a swept frequency signal are passed through to a narrow band FM descriminator, the output of which is amplified by a unidirectional amplifier. The output of the amplifier, present when a signal is received, is utilized to momentarily slow the frequency swept local oscillator resulting in a time expansion of the characteristic S-shaped descriminator output signal. This results in the generation of a negative-going error signal between the two time expanded halves of the S-shaped descriminator response. The error signal when amplified produces a significant voltage spike which ensures reliable detection, to permit the detection of a single radar pulse with a reduced false alarm rate.