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Rev. A00 HQ-ST System Manual Page 3 of 32
Figure 4: ST Plus: rear connections
HQ Plus
The HQ Plus operates as a TCP/IP Raw Server, with a known IP:Port address. The HQ Plus is intended to provide a head-
office serial-to-Etherenet interface for a polling application to access remotely located device to be polled.
The HQ Plus provides a modem-like serial interface (US Robotics (USR) command set, DB-25F connector), that is used
by an external device such as a PC to make a "telephone - modem" call (that is, using a conventional modem dialing
string of the format: ATDT5551234).
The HQ Plus comes in versions that support up to 126, 30, or 8 ST sites.
Figure 5: HQ Plus-126, HQ Plus-30, HQ Plus-8
A set of LEDs on the HQ Plus indicates the status of the serial ports of the device, and the number of active ST Plus
connections.
Figure 6: HQ Plus LEDs
The number of active connections has a binary representation. When there are no active connections, the connection
LEDs light and unlight in sequence, creating a “bit walk”. When connections exist, the number of connections is
represented by the sum of the values in each box above. For example, if the “64”, “4”, and “1” LEDs were lit, the number
of active connections would be 69.