TR-1710/DAIR General Principles of Operation The Model TR-1710/DAIR is a 10-channel magnetic tape recorder/reproducer system. Cannel 5 is used to record and play back the selective identification feature (SIF) replies from Interrogator Set AN/TPX-42A(V) DAIR (Direct Altitude and Identity Readout). The SIF information is derived from Video Signal Processor CP-1045/T. The reproduced SIF information is directed to Indicator Data Processor CP-1047/T. Both of these equipiments are part of the AN/TPX-42A system. Channels 1-4 and 6-9 are used to record and reproduce audio information. Channel 10 is normally used to record a time code signal, although it can be used to record audio data, if desired. A simplified block diagram of the unit is shown in figure 1-2. Audio signals to be recorded are applied to the record amplifiers, where they are amplified to the proper level and applied to the multichannel recording tape through the recording head. SIF binary data are applied to a record converter assembly which converts the incoming frequency shift keyed (FSK) signal to a biphase signal for recording. The SIF data recorded on channel 5 are applied to a reproduce converter assembly which converts the biphase recorded signal back to the original FSK format. The recording, reproducing, monitor, and fail-safe amplifiers and the record converter and reproduce converter are modular plug-in units containing all solid- state circuitry. The modular design is also employed for the power supplies and magnetic heads, thus permitting rapid replacement and minimun downtime in the event maintenance is required. The unit contains two identical tape transport assemblies, one of which may always be kept in standby condition. A fail-safe control tone is continuously recorded and reproduced at a level well below that of the desired voice recording. If the reproduce head does not pick up this signal and if the fail-safe amplifier does not detect the control tone, recording is automatically switched from the operating transport to the standby transport. A shorting tab generates a control signal when most of the tape has been used and this signal switches the recording from the used- up transport to the standby transport. The main power supplies for the unit are also duplicated. Automatic transfer between the two power supplies is effected at the same time as transport changeover. The record converter and reproduce converter use a separate regulated power supply. Another feature of the tape transport is the straight-line threading mechanism which, in addition to simplifying the threading operation, also keeps the tape loop tight. This is accomplished by having a slight diameter differential between the driving capstan (lower) and the holding capstan (upper). Because of the duplication of tape transports, the unit may be used for monitoring a previously recorded signal on one transport while the other transport is recording. However, this is done only when it is not necessary to have the extra reliablility provided by the second transport in standby. New tapes may easily be loaded on the transports and whenever the information recorded on a tape is no longer required, the tape will automatically be erased as it is used for making a new recording. Any on of the nine audio channels can be individually monitored on either of the two transports. Either the PHONE jack or the monitor loudspeaker may be used. A rotary switch allows the operator to monitor either the incoming signal or the reproduced signal (which occurs approximately 2 seconds after the recording is made). Each transport is designed to carry the tape in a "fast-forward" or "fast-rewind" mode as desired. In either of these modes, the erase head is not energized and the tape is not touching any of the three heads. The CUR switch energizes a solenoid which causes the tape pressure arm to move the tape into position over the heads so that the operator may search for time at high speeds with some of the optional digital time systems. As previously stated, it is normal practice to use on of these channels to record an audio time announcement. The Magnasync Time Code Generator System is recommended for this purpose; however, any high-quality audio time announcer with matching characteristics may be used.