The Protocol - Nov/Dec 1998

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FDO 3000 Off-Net Takes Order-Wire Public

The FDO 3000 Off-Net interfaces DPS' FDO 1000-series Order-Wires to the public switched telephone network (PSTN) via 2-wire or 4-wire line. Microprocessor control of the FDO 3000 brings maintenance communications into the 21st century.

DTMF Selective Signaling

The DPS FDO Off-Net uses its on-board microprocessor to synthesize and decode DTMF signaling tones. The Off-Net can be programmed for automatic privacy, manual privacy, no privacy and "hoot-n-holler'' modes.

FDO 3000

Companion Order-Wire

The FDO 3000 Off-Net is normally installed adjacent to an FDO 1000 Order-Wire terminal. The off-net interfaces the order-wire network through the 4-way passive bridge on the order-wire. lf the off-net is used in a digital network, its voice signal is converted to digital by an Adaptive PCM (ADPCM) card in the order-wire housing.

Digital Interface

The FDO 3000 Off-Net can be equipped with a DVF-64 digital interface card in the expansion card slot. This interfaces a 24 Kbit port to the ADPCM card in the order-wire.

LED Indicators

Front panel LEDS indicate order-wire off-hook, incoming call ringing and channel busy. Front panel test points and level controls allow calibration while the unit is in place.


The Off-Net responds to one, two or three digit addressing. Leading zeroes in the address will set it for one or two digits. Rotary switched on the P.C. board allow the address to be easily set. The station address is posted on the front panel with stick-on labels (labels are included).

Network Control

In privacy modes, the FDO 3000 generates DTMF tones to control access to the order-wire network.

When an off-net caller calls the off-net while the order-wire network is in the busy state, he will hear a busy signal. lf he calls while the network is un-busy he hears dialtone and an off-hook tone is generated to the order-wire network. This causes other stations on the network to assume a busy state. lf any order-wire station phone is picked up during the busy state, a busy signal will sound in the earpiece. Stations that are busied remain in that state until their station code is dialed from the caller's phone or until the caller hangs up, generating an on-hook tone.

Order-wire stations call the off-net by dialing a one, two or three digit code, like any other station. The off-net seizes the PSTN line and returns dial tone from the central office or PBX. The caller then dials an off-net number as though he were using a regular phone. Upon completion of the call, the off-net sends an on-hook tone to the order-wire to reset the busy state.

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