Block Diagram of The GSGC25 as an Adobe .pdf drawing

 The GSGC25 has an inbuilt three channel mixer, each of the channels are mic/ line switchable and have +12v phantom power available. Each of these channels has a gain control, large on/off pushbuttons & an on indicating LED. The mixed output of these channels are fed through a compressor/ limiter and are sent to the program line Codec, this output is also on a rear panel ‘bantam’ jack. There is a 7 LED PPM for indication of the mixer output level.

 A momentary talkback button (which also has a permanent on (Lazy) switch), switches the 3^rd input of the mixer to the talkback line Codec, this talkback also appears on a rear panel ‘bantam’ jack. An indicating LED shows when talkback is in use.

 Monitoring is provided from 4 sources, each with it’s own level control and each can be switched to both (left & right) or either (left or right) channels of the headphone amplifier. These 4 sources are: TALKBACK from the 2^nd Codec or from a rear panel input on ‘bantam’ jack: CUE the return feed of the program line Codec: EXT a local external input on rear panel ‘bantam’ jack: MIX the output of the mixer. The headphone amp output is on three front panel A/B gauge headphone jack sockets, one wired to only the left channel of the headphone amp, one wired only to the right channel & one wired to both. The headphone amplifier is for headphone impedances of 200 to 2000 Ohms.

 A record output (on a rear panel ‘bantam’ jack) is a mix of the output of the GSGC25’s mixer and the return programme cue line.

 For ISDN line dialling, answering and Codec set up functions a front panel keypad is provided. A 3 position toggle switch, switches this keypad to control either the programme line, the talkback line or a safe function that prevents the keypad from being used accidentally. Each of the 2 G722/ G711 Codecs has a large green LED to show when Codec lock is O.K. and also a large red LED to show when an ISDN line is open.

 The GSGC25 can be powered from 2 ‘D’ cells (approximate battery life of 4 hours) or an external plug top psu. If it is being powered from the external supply and the supply fails the batteries will automatically take over. A front panel LED shows when the GSGC25 is switched on and flashes to indicate when battery level is low.

GSGC24A
The GSGC24 is a simpler version of the GSGC25, designed primarily to be extremely easy to use for non technical staff. It utilises only one of the G722/ G711 codecs, has no talkback channel or external input.

Links to Other ISDN Pages

GSGC5       GSGC6      GSGC8     GSGC9    GSGC17  GSGC24A   GS3U-057    TX RESERVE