GLENSOUND GS-FW035 INTERCOM Desktop, 1x 4-wire circuit, with PTT

These are rugged designs intended for the rigours of outside broadcasts. The aluminium cases have overhang protection of the front controls and belt clip.

GS-FW008 - 1x 4W circuit - IFB, 1x stereo cue in

This has a microphone input, with 12V phantom power, which may be switched to suit a line level signal, a 3-way talk switch and a headphone socket. A stereo programme input, 6.35mm jack socket, 47k ohms, may be switched to feed the 4-wire output interrupted by the talk switch or to a stereo auxiliary output again a 6.35mm jack. Power: 1x PP3 or external 12-20V DC.

GS-FW021 - 1x 4W circuit - IFB - 1x auxiliary input - 2-wire mode compatible

This has a microphone input without gain control and mono headphone output, both sharing a 6.35mm 3-pole jack socket. PTT switch; the 4-wire output can be fed with the incoming 4-wire signal when the PTT switch is not pressed. A 2-pole 3.5mm jack socket provides an auxiliary input to feed the headphones. Power: 1x PP3.

All these are 1U high. All have a panel microphone and a panel loudspeaker. On the rear are the 4-wire circuits and an IEC inlet for power: 230V AC nominal.

GS-FW018 - 1x 4W circuit - IFB, 1x cue in

This has a single 3-way talk switch. A rear-mounted XLR input provides a programme input. Two switches next to the talk switch select the programme and 4-wire inputs to feed the 4-wire output when the talk switch is in the centre position. Two controls set the level of the two inputs heard in the speaker and headphones.

GS-FW024 MKII - 4x 4W circuits - IFB, 1x cue in

This has four 3-way talk switches. A rear-mounted XLR input provides a programme input. Two switches next to each talk switch select whether the programme input or the 4-wire input or nothing is sent to the 4-wire output when the talk switch is in the centre position. Controls next to each talk switch set the level of the incoming 4-wire signals heard in the speaker and headphones; a further control sets the level of the programme.

GS-FW031 - 2x 4W circuits - IFB, 1x cue in

This has two 3-way talk switches. A rear-mounted XLR input provides a programme input. Speak on/off control is via sprung keys. Two switches allow the user to switch between program and interruptible foldback, I/P and 4wire. A third control allows control over mix and cut.. Controls next to each talk switch set the level of the incoming 4-wire signals heard in the speaker and headphone.

These take a a number of 4-wire circuits, and derive a 2-wire feed from them, which can be used to feed other systems such as third-party intercoms.

GS-FW004 - 1x 4-wire circuit - Passive, free-standing

This has a single 4-wire connection which must be connected to equipment with low source impedance, 50 ohms or less, and high input impedance, 10k ohms or greater. It provides a 2-wire output, presented on both male and female 3-pole XLR connectors, wired in parallel. The 2-wire connection must be terminated in 600 ohms.

GS-FW006 - 3x 4W circuits - Rack mounting

This is contained in a 1U rack mounting case, and has three primary 4-wire circuits on the rear. Each primary circuit has an associated 2-wire connection and a secondary 4-wire circuit on the rear. Three switches on the front panel route the primary 4-wire circuit to either the secondary 4-wire circuit or the 2 wire connection. Power: 230V AC nominal, rear IEC inlet.

4 Wire Circuit - 4W circuit

This is a term used here to describe communication between units using two separate balanced audio circuits; one to each unit, one from each unit. Unless otherwise described, a '4-wire circuit' means a balanced input using a 3-pole female XLR connector and a balanced output using a 3-pole male XLR, both at nominally 0dB.

2-Wire

A balanced audio circuit, containing a mix of both send and receive signals.

IFB

An acronym for interruptible or interrupted feedback or foldback, sometimes also known as 'programme cue interrupt', 'switched talkback' and 'interrupt for broadcast'.

Unless otherwise described, it is used here to mean a facility to receive an audio signal - commonly a feed of the programme, possibly interrupted by an upstream talkback unit to inject voice communications - and to send that signal out on the 4-wire output, interrupted by a local talkback microphone when a talkback button is operated.

Headphone socket

Unless otherwise described, this is used here to mean a 6.35mm, 3-pole jack socket providing an output to headphones with an impedance of 200 ohms or higher. Unless otherwise stated there is an associated volume control, which, in desktop and rack mounting designs will be shared with a panel loudspeaker.

Microphone input

Here this means a female 3-pole XLR connector feeding an input suitable for a dynamic microphone of 200 ohms or greater impedance. There is an associated gain control. If phantom power is available, it may be used with condenser or electret types with appropriate powering requirements.

Panel microphone

Rack mounting and desktop designs have a stub microphone, unless otherwise described, mounted on the panel facing the user. This is accompanied by a 3-pole female XLR socket; an alternative microphone input selected by a switch.

Panel loudspeaker

Rack mounting and desktop designs have a loudspeaker, unless otherwise described, mounted on the panel facing the user, with a volume control shared by a headphone socket, which deactivates the speaker when a jack is inserted. The speaker is dimmed when a talk key is operated.

'Talk' switch

This used here to mean a switch which is operated when the user wishes to talk to units fed from the 4-wire output. Several types are used by these designs.

Three position talk switch - '3-way talk switch'

This locks in the 'up' and centre positions. Pressure must be maintained on the switch to hold it in the 'down' position. In 'up' and 'down' positions, the local talkback microphone is sent to the 4-wire output. In the centre position nothing is sent to the 4-wire output unless the unit has an IFB facility.

Momentary talk button - 'PTT switch'

Pressure must be maintained on the switch to hold it in the 'on' position, sending local talkback to the 4-wire output. When released, no talkback is sent to the 4-wire output unlesss the unit has an IFB node, in which case the incoming 4-wire signal can be sent to the 4-wire output.

XLR input

This is used here to mean a balanced, line-level, input using a female 3-pole XLR socket.

XLR output

This is used here to mean a balanced, line-level, output using a male 3-pole XLR socket.