The State of the Art Simplex Interconnect
Communications Electronics Specialties introduces the CES 510SA "Smart" Simplex Autopatch, with many important new features never available before: * Three digit control codes with user programming. * A sophisticated toll restrict provides positive long distance lock out, * Time-out and COR actJVity timers with warning beeps and digital programming, • Rotary or DTMF dialing. * Phone Irne in-use detector prevents |Hf interrupting a call in progress, and sends unique CW sequence. * Phone ring detection logic enables unique CW sequence * Digital programming of the sample rate and width, and noise gate sensitivity control, lor easy interfacing with most radios. Simple and direct connections to radio.
Options available: * Smart CW identifier with unique CW messages for each patch function. • FCC type accepted phone line coupler. * Special tone squelch kit to operate patch through repeaters.
The 510SÀ —the newest advance in interconnect technology, from the innovators at:
Communications Electronics Specialties, Inc.
Post Office Bo* 507 * Winter Park, Florida 32790
(305) 645-0474 • Toll-free (for orders only): (800) 327-9956 . ^
able number of SYN characters will be transmitted between data blocks. Depending upon the speed of the receiving computer, any number between 1 and 10 SYN characters might be required to allow adequate processing time at the receiver. The number of SYN characters transmitted between blocks can be varied to suit the sending or receiving operators. A certain minimum number of char* acters will be necessary to al low the receiving computer enough processing time, but any number of additional SYN characters will not disrupt the scheme, since the receiving computer will simply wait until it encounters an SIX character to start processing the next data block The on!y effect of sending more SYN1 characters than actually needed will be to reduce data throughput below the optimum for that combina tion of computers
Another reason to allow varying the number of SYN characters is that we want to be able to use this scheme over a variety of actual data rates. Since the computer processing time wil) remain fixed while the character transmission time may change considerably, it will be advantageous to use fewer synchronizing characters at the lower data rates and more at the higher data rates to allow the same processing time at the receiving computer
This system does not lend itself weil to informal conversation at low typing speeds and would primarily be of use after initially establishing contact with another station and mutually deciding that a large block of data (perhaps 100 formalmessages) is to be transferred. At this point, both stations would switch to the block-encoded mode to transfer the data.
Once in the block-encod ed mode, we would begin a transmission with a leader of SYN characters perhaps 5 seconds long. The remainder of the transmission would consist of ACK or text blocks. We will require that the text blocks be transmitted sequentially, but we wilt allow the ACK blocks to appear anywhere during the transmission Since we wttl not be using error-detection on the ACK blocks, it will be a good idea to send the ACK blocks more than once to make sure they are received correctly Between blocks any number of SYN characters may be transmitted. The last block of the transmission will be followed by several SYN characters and then the five ETB characters to signal the end of transmission.
How can diversity operation help us in this scheme? If a receiving interface is available where the mark and space frequencies can be detected independently, the receiving computer can treat the two frequencies as separate signals, and we get fwo chances for each data block to be received correctly. If either the mark or space channel produces an error-free block, the receiving computer can ACK that block. This ciin greatly reduce the number of retransmissions under moderately degraded conditions and greatly increase throughput.
I have described one of several possible methods to achieve error-free transmission of digital data over a very imperfect radio channel by using error-detecting coding, ARQ, and computers at each end of the radio link. I hope these ideas will help to get some experimenting underway in this direction ■
Introducing The SRT-3000
• Built-in demodulator & AFSK modulator for 170,425,850 Hz shifts, high and low tone pairs • 60,66,75,100,132 WPM Baudot, 110,300 Baud ASCII, 5-99 WPM Morse • 1000 character text buffer with BREAK feature • Ten 80 character message memories with battery backup •
SRT-3000 List Price $ 995.00 INTRODUCTORY PRICE $ 795.00*
Selectable display formats, 24 lines x 72 characters (2 pages), 24 lines x 36 characters (4 pages), 16 lines x 36 characters (6 pages) * Split screen operation • On screen status line displays a tuning bar, mode, speed, shift, tone pair, normal/reverse, USOST WRU, SELCAL, buffer mode and buffer count * Cassette interface for long "Brag Tapes" or unattended message storage • Baudot and ASCII printer outputs * Built-in audio monitor • Built-in 110 VAC power supply • Other features—PTT control, WRU, SElCAL, sync idle, CW ID, USOS, autostart, full or haft duplex, scope outputs, weight control, intercharacter spacing, reverse video, RS-232, word wrap around * Compact size only 13.3 x 10.3 x 4 inches * Made in USA,
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787 BRIAR LANE, BELOIT, WISCONSIN 53511
'introductory prices good thru Feb. 28. 1983L Optional 9' video monitor shown $149.00.
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