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1.2 DESCRIPTION OF EQUIPMENT
1.2.1
Functional Characteristics
The Model F271XA Telephone Modem is an extender for subscriber (telephone handset)
connected telephone lines. These units are designed to be used with Model F270XA, which supply
an exchange (PBX or direct dial service from a telephone company) interface. When configured
in this way, the modems provide a fiber optic link for regular, 2-wire analog telephones. The main
characteristics of the Model F271XA are:
Transparent extension of telephone lines.
SFP Based optics.
Supports data up to 14.4kbps via dial-up modem or facsimile.
Model F270XA and F271XA modem pairs use SFP optic modules to achieve transmit
distances of up to 20km over a single pair of fiber-optic cable. Alternatively, these telephone
modems can be used in a VMX20 Versimux II chassis, which can multiplex up to 19 telephone
modems on a single pair of fiber-optic cables.
1.2.2
Audio Transmission Characteristics
The F271XA accepts a telephone audio signal on the RJ11 connector from the subscriber,
digitizes it with an analog-to-digital converter. The digital samples are then encoded and applied
to the SFP for transmission over the fiber-optic cable.
The remote F270XA unit decodes the signal from the SFP module, and applies the samples
to a digital-to-analog converter to recover the analog audio. The converse occurs in the other
direction for the F271XA.
The telephone modem transmits analog signals of 300 to 3400Hz.
1.2.3
Physical Characteristics
The telephone modems measure 7.0" wide x 0.84" high x 11.6" deep (17.8 x 2.1 x 28.9 cm)
and are designed to be mounted in a variety of VERSITRON enclosures and chassis (see Table 1
for dimensions of enclosures and chassis). "Desktop" option is a single-card enclosure. Rack-
mount options include a 2-Slot and 20-Slot 19” standard rack-mountable chassis. For either
desktop enclosure or 2-Slot rack-mount chassis, each F271XA unit requires a wall transformer,
VERSITRON Model PSAC08 (US) or PSAC09 (European), providing 12 VDC, 1.0A. The one-
pin power connector for electrical input is on the back of the card. There is a RJ11 jack for the
telephone line on the front of the card. There is an SFP module slot on the back of the card for the
SFP fiber-optic interface. For HF-20A chassis installations, power is provided by VERSITRON
Model AC300WR Power Supply / System Monitor, through the twelve pin connector (P1). For
Versimux II installations power is provided to the VMX20 chassis by VERSITRON Model
AC300WR Power Supply / System Monitor, through the twelve pin connector, and the link
connection is provided by the backplane connector (J5). In Versimux II installations the SFP
module will be deactivated, and link communications will occur over the backplane connector J5.
Therefore, the SFP need not be populated in Versimux II installations. Both F270XA and F271XA
models have eight indicator LEDs as described in Table 2.
