10.0 Part Line, Technical Concept; 11.0 Technical Specifications Ps 19A - ASL INTERCOM PS 19 A User Manual

10.0 PART LINE, TECHNICAL CONCEPT
User stations and power supplies in an ASL
intercom system are connected via one or several
'party lines'.
A party line offers two way ('full duplex')
communication and consists of standard
microphone (multi-pair) cable. One wire is used
as an audio line, one as a power line and the
screen of the cable functions as earth/return.
Current drive is used for signal transfer.
Each station utilizes a current amplifier to amplify
the microphone signal. That signal is put on the
common audio line.
Due to the constant line impedance, a signal
voltage is developed which can be further
amplified and sent to the headphones or
loudspeakers.
11.0 TECHNICAL SPECIFICATIONS PS 19A
System
Dynamic range: 80 dB (1 kHz, THD , 1%)
Call signal: 2.8 mA
Call signal threshold (receive): +2.4V DC
Supply voltage: + 30V DC (12 – 32V DC)
Power interrupt time (mic mute): 0.1 sec
Intercom party line
Impedance: 350 Ω (1 kHz) / 2.2 kΩ (DC)
Audio level: nom. -18 dBu, max. +4 dBu
Mic pre-amp
Headset mic. impedance: 200 Ω
Gain: 40 – 60 dB (adjustable internally)
Presence filter: +6 dB at 5 kHz
Frequency response: 200Hz - 15 kHz (-3 dB)
Power to electret mic: +9V DC
Headphone Driver Amps
Max output level: 14 Vrms @ 200 Ω
Max output power: 2x 0.28 Wrms @ 400 Ω
Side Tone
Rejection: 0 – 30 dB adjustable
Buzzer
Max. SPL: 85 dBA
(The line impedance is situated in the power
supply between XLR pin 3 and 1)
This principle has three advantages:
o the use of a single audio line allows
several stations to talk and listen
simultaneously
o due to the high bridging impedance
offered by each station, the number of
stations on the party line has no influence
on the level of the communications audio
signal
o power and audio to the intercom stations
use the same cable
Also the Call signal is sent as a current, on
the audio wire. It develops a DC potential over
the line impedance which is sensed by each
intercom station and interpreted as a Call
signal.
PGM input
Input impedance:
30 kΩ (balanced line level)
4.6 kΩ (balanced mic level)
Nominal input level:
-18 dBu to +6 dBu (line level)
-38 dBu to -14 dBu (mic level)
Max. input level:
+22 dBU (line level)
+2 dBu (mic level)
PS 19A Power Consumption
Current (at 30V DC):
30 mA quiescent
45 mA signaling
170 mA at max. output + signaling
PS 19A Dimensions & Weight
Width: 90 mm
Height: 38 mm
Depth: 124 mm
Weight: 310 grams
0 dB is defined as 775 mV into open circuit
ASL reserves the right to alter specifications
without prior notice