Abstract: Time Division Multiple Access (TDMA) is being utilized widely in domestic and international communication networks. The types of TDMA networks in operation fall into two categories: Wideband and Narrowband. In the past few years, a number of Wideband and Narrowband TDMA networks have gone into operation. However, these networks have typically operated as independent nets. As the existing Wideband TDMA networks expand into cities with a smaller amount of originating traffic, a major economic problem occurs. It becomes difficult to justify the cost of a Wideband TDMA station for the smaller amount of traffic.This invention presents an approach that solves the above problem by providing an integrated network with Wideband TDMA for the large cities and Narrowband TDMA for the smaller cities.

Abstract: Apparatus for maintaining a transmit radio signal frequency in a predetermined frequency relationship with a received radio signal. A common voltage controlled frequency source serves as an Lo signal generator for both the receiver and transmitter. A reference frequency oscillator is phase compared with a receive IF signal to derive a control voltage for the voltage controlled frequency source. The resulting phase lock loop provides transmit signal frequency control with respect to a received signal.

Abstract: Digitally encoded (DPCM) NTSC video is transmitted in a standard T3 data format and rate via a transmit interface module. The module is subjected to inputs comprising DPCM encoded NTSC video, horizontal sync and a video sampling clock at 3f.sub.sc, where f.sub.sc is the color subcarrier frequency. The sampling clock is used to write the DPCM encoded video and horizontal sync into a buffer. The buffer is read out via a read clock which is a submultiple of the 44736 MHz T3 rate. To assist in receiver decoding, the video data is supplemented with horizontal sync indicating code words, which designate the start of each horizontal scan line. On detection of a horizontal sync word read out of the buffer memory, the read clock is inhibited for the insertion of the horizontal sync indicating code words. The T3 frame is also supplemented with two digitized audio channels, stuff indicators and a stuff opportunity slot as well as parity, frame and multiframe indicators and an alarm channel.

Abstract: An injection laser is turned on and off in response to DATA and DATA control signals. A photodiode is irradiated by the laser and passes current that is proportional to the intensity of the laser radiation. A current switch responds to the DATA signal to define a current path for the source current of associated source current transistors when the laser is on. A difference current, corresponding to the difference between the photodiode current and the source current, is then applied to an integrator. The integrator generates an error signal corresponding to the difference in charge transfer between the photodiode and the source current transistors. The error signal is applied to operate a bias transistor that generates a corresponding DC bias current for the laser.