The LST1 is a non voice-switched loudspeaking telephone instrument which is powered by exchange line current. It consists of three parts: a 708 two-tone grey table telephone containing a loudspeaker in place of the dial; a light-grey control unit incorporating a microphone, dial, on/off key, a volume control and a light which shows when it is switched on; and a wall mounted amplifier unit which is mounted in a light grey plastic case.

The LST1A is a non voice-switched loudspeaking telephone instrument which is powered by exchange line current. It consists of three parts: a 716 two-tone grey table telephone containing a loudspeaker in place of the dial; a light-grey control unit incorporating a microphone, dial, on/off key, a volume control and a light which shows when it is switched on; and a wall mounted amplifier unit which is mounted in a light grey plastic case.