Telephone Expansion Board (FXO) (700-15-03)

Telephone Expansion Board (FXO) (700-15-03)

Optional Telephone Expansion Interface for Mercury Interface Units (MIUs)

  • Provides a standard interface for up to 4 PSTN lines or other third-party telephony devices
  • Up to 4 Telephone Expansion Boards per MIU
  • Allows outside callers to access the Mercury system and reach individual subscribers or conference automatically or via an operator
  • Enables Mercury users to make and receive outside phone calls from anywhere on the system
Item Part Number:


The Telephone Expansion Board (FXO) is an optional interface board that provides a standard interface for Mercury hardware panels and third-party telephony systems, like PSTN lines, PBXs, cellular telephone interfaces and other telephony devices.

Technical Specifications

Line Interface

Number of channels: 4 per card, Max of 4 option cards per MIU

DSP Channel usage: 4 DSP IP channels per card, regardless of whether the channel is routed to a different host

Signaling: Loop start or ground

DTMF: DTMF detection for DDOI routing

Bypass phone operation: Phone is switched out of circuit whenever FXO channel is in use

Line Impedance: CTR21, 600R, 900R or Japan – software selectable

Return loss: >18dB 300-400Hz

Protection: FCC pt 68 type B longitudinal surge, 1500V: FCC pt 68 type B metallic surge, 800V

Ring equivalency number: REN <0.2

Longitudinal balance: >60dB (200-1000Hz); 40dB (1000-4000Hz)

Common mode rejection ratio (CMRR):
On hook >70dB 50-500Hz Vcm=60Vrms

Off hook >40dB 50-500Hz Vcm=60Vrms

Common mode overload level (CMOL):
On hook >300Vrms 50-60Hz

Off hook >250Vrms 50-60Hz

Max trip/ring voltage: 300V (Correct operation not implied) Recommended max 120V

Max loop current: 90mA

Ringing voltage – detect: Typically 22V, min 26V, 17-68Hz

Ringing voltage – no detect: Typically 14V, max 18V, 1768Hz

THD: <1% at 0dBm, 1kHz

Crosstalk: <-85dB (inter-channel and inter-card)

Insertion Loss: 0dB

Nominal line TX level: -9dBm ± 1dB

Input level adjustment Via software: –9dB to +12dB in steps of 1.5dB

Output level adjustment Via software: –34.5dB to +12dB in steps of 1.5dB. Mute option

Freq response: 300Hz – 3200Hz ± 2dB ref to 1kHz (8kHz sampling)


Line: RJ11 2 pin modular jack socket

Bypass Phone: 1 per channel (4)

Phone connector pinout: Pin 3 – tip (B), Pin 4 – ring (A), other pins – unused


Ring Cadence: US Ringtone

Echo Suppression

General: DSP Based adaptive filter providing acoustic & network suppression

Tail length: (acoustic) 63.5ms

ERLE: 30dB typical


Operating Temperature:
32° to 122°F (0° to 50°C)

Storage Temperature:
-4° to 185°F (-20° to 85°C)

Operating Humidity: 0 to 90%, non-condensing, relative humidity


5.5 x 0.67 x 8.1in (WxHxD)

(140 x 17 x 205mm)


7.1oz (200g)


MTFB: 80,000 hours

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