The HA2400LP is designed for those applications where no external source of power is available. The HideAway derives its power from two isolated sources:
Power from the RS232 interface (TXD, RTS & DTR) activates the HideAway's RS232 drivers, the AT Command set controller and the optical relay that picks up the telephone line; Power from the telephone line then activates the data pump and ancillary telephone line components
jump to HideAway Manual PDF file
HideAway is uniquely designed to adapt to a wide range of applications in the commercial and industrial environments. Current users include manufacturers of equipment which require remote diagnostics and maintenance. They include utility and telephone companies, test and diagnostic equipment and PBX manufacturers, who require remote access to their equipment for maintenance and data acquisition.
HideAway is also used by companies providing special services and equipment such as energy management and security services. HideAway could be installed in an energy management unit, enabling it to report energy consumption of a remote site to a host.
Since the HideAway is a full duplex two way modem, it may receive or initiate a call. Despite its miniature size of 2.2" x 3" x .83" and its weight of less than 2.3 ounces, HideAway is as powerful as larger desktop modems. Neither the size nor the low current requirements, effects the superb performance of this unique device.
HideAway is fully Hays compatible. It complies with CCITT standards V22bis and V22 as well as Bell 103 and Bell 212A protocols. HideAway is a smart, rate adaptable modem that adjusts itself to the data rate of the corresponding modem.
The heart of the HideAway's circuit is its power "scavenger" that derives power from two isolated sources: the telephone line and the RS-232 pins.
NOTE 1 - It is essential, that the RS232 connection to your HA2400LP provides TD, RTS & DTR signals from which the HA2400 can draw its initial operating power, and that the unit is connected to a dial-up, not leased, telephone line.
Electronic data communications between elements will generally fall into two broad categories: single-ended and differential. RS232 (single-ended) was introduced in 1962, and despite rumors for its early demise, has remained widely used through the industry.
Independent channels are established for two-way (full-duplex) communications. The RS232 signals are represented by voltage levels with respect to a system common (power / logic ground). The "idle" state (MARK) has the signal level negative with respect to common, and the "active" state (SPACE) has the signal level positive with respect to common. RS232 has numerous handshaking lines (primarily used with modems), and also specifies a communications protocol.
The RS-232 interface presupposes a common ground between the DTE and DCE. This is a reasonable assumption when a short cable connects the DTE to the DCE, but with longer lines and connections between devices that may be on different electrical busses with different grounds, this may not be true.
RS232 data is bi-polar.... +3 TO +12 volts indicates an "ON or 0-state (SPACE) condition" while A -3 to -12 volts indicates an "OFF" 1-state (MARK) condition.... Modern computer equipment ignores the negative level and accepts a zero voltage level as the "OFF" state. In fact, the "ON" state may be achieved with lesser positive potential. This means circuits powered by 5 VDC are capable of driving RS232 circuits directly, however, the overall range that the RS232 signal may be transmitted/received may be dramatically reduced.
The output signal level usually swings between +12V and -12V. The "dead area" between +3v and -3v is designed to absorb line noise. In the various RS-232-like definitions this dead area may vary. For instance, the definition for V.10 has a dead area from +0.3v to -0.3v. Many receivers designed for RS-232 are sensitive to differentials of 1v or less.
This can cause problems when using pin powered widgets - line drivers, converters, modems etc. These type of units need enough voltage & current to power them self's up. Typical URART (the RS-232 I/O chip) allows up to 50ma per output pin - so if the device needs 70ma to run we would need to use at least 2 pins for power. Some devices are very efficient and only require one pin (some times the Transmit or DTR pin) to be high - in the "SPACE" state while idle.
An RS-232 port can supply only limited power to another device. The number of output lines, the type of interface driver IC, and the state of the output lines are important considerations.
The types of driver ICs used in serial ports can be divided into three general categories: